Pokémon HeartGold and SoulSilver/Breeding
To breed Pokémon, you must leave two Pokémon in the Pokémon Day-Care centre. The Day-Care in Red, Blue, and Yellow is located south of Cerulean City on Route 5. In FireRed and LeafGreen, it is located on Four Island of the Sevii Islands. The Day-Care in the Johto region is located south of Goldenrod City, on Route 34. The Day-Care centre in the Sinnoh Region is located in Solaceon Town, and the Day-Care in the Hoenn Region is located west of Mauville City, on Route 117. In Generations 2 and 3, the egg will hatch into a Lv. 5 Pokémon. In Generation 4, the egg will hatch into a Lv. 1 Pokémon. If you deposit two Pokémon in the Day-Care, there is a possibility that that they may leave an egg, depending on the circumstances.
- Both Pokémon must be in the same Egg group. If two different Pokémon are used in the breeding process, the baby Pokémon will be the same species as the mother.
- There must be one male and one female (unless the Ditto Rule is used).
The Pokémon must be given enough time to breed. This time will vary. The Old Man standing outside the Day-Care will tell you how well the two Pokémon get along. The better the Pokémon get along, the faster an egg will appear, if ever. He will respond with one of the following phrases, indicating the chances of producing an egg:
- They seem to get along well: 70%
- They seem to get along: 50%
- They don't seem to like each other: 30%
- They prefer to play with other Pokémon: 0%
After this is said, start walking. After a certain number of steps, if the conditions are right, an egg will be produced. Regardless of the percentage, if they have a base chance higher than 0%, enough steps will get you an egg. The resulting Pokémon should be the lowest evolved form of the female, but there are some exceptions to this:
- A female Nidoran's egg could result in either a male or female Nidoran.
- An Illumise's egg could be an Illumise or a Volbeat.
- An Azumarill or Marill egg will usually be a Marill.
- A Wobbuffet's egg will usually be a Wobbuffet, not a Wynaut.
 The Ditto Rule
The one Pokémon that ignores the second rule is Ditto. A Ditto can be used instead of a second Pokémon. Some Pokémon are genderless, like Bronzong, and can breed with a Ditto and will hatch into a Bronzor. Other species like Nidoran♂ are male-only, and thus breeding with a Ditto will yield a Nidoran egg. Any Pokémon not in the unbreedable group can breed with a Ditto.
 Item effects on eggs
When breeding a female Wobbuffet or Azumarill (or Marill) the egg will generally hatch into the same Pokémon. But, a Wobbuffet with a Lax Incense will produce a Wynaut egg. Similarly, an Azumarill or Marill with a Sea Incense will create an Azurill and a Snorlax with a Full Incense will produce a Munchlax. This is known as the Incense Rule. Items can have various effects on the Pokémon in the egg. Some Pokémon will inherit moves or natures from their parents, for example, a Pikachu holding a Light Ball will produce a Pichu that knows Volt Tackle, or a Ditto and a Parent holding an Everstone have a 50% chance of producing a Pokémon with the same nature as the Parent. For other items and their effects see the item sections.
 Inherited/Egg moves
When breeding, the Pokémon that hatches from the egg will be the same species of the mother (except when the Ditto Rule is applied). The egg Pokémon usually inherits moves from its father. There are several ways a Pokémon can inherit moves. Inherited moves are moves that a Pokémon would not normally learn, but inherits through breeding.
- If the father has learned a TM move, the baby will hatch knowing the TM move, assuming it is capable of learning that move.
- If the father knows a move that is on the offspring's egg move list, (a list of moves that can only be learned through breeding) then the baby will be born with the egg move.
- If both parents know a specific move on the baby's level-up move list, then the baby will hatch knowing that move.
 Quick Hatching
In Emerald, FireRed, LeafGreen, Diamond, Pearl, Platinum, HeartGold, and SoulSilver, if you carry a Pokémon with the ability Magma Armour or Flame Body in the party slot next to the egg, the number of steps needed to hatch the egg is halved.
 Baby Pokémon
Baby Pokémon were introduced in the Generation II games as pre-evolutions to existing Pokémon, and are usually only available by breeding. These baby Pokémon are listed below:
- Mime Jr.
- Riolu (even though Lucario wasn't introduced in Generation III)
 Incense Rule
If certain species of Pokémon hold a certain incense when breeding, then you will get its baby form. There are quite a few Pokémon that can do this:
- Marill or Azumarill with Sea Incense to get Azurill (Gen. 3 and 4)
- Wobbuffet with Lax Incense to get Wynaut (Gen. 3 and 4)
- Roselia or Roserade with Rose Incense to get Budew (Gen. 4)
- Chimecho with Pure Incense to get Chingling (Gen. 4)
- Sudowoodo with Rock Incense to get Bonsly (Gen. 4)
- Mr. Mime with Odd Incense to get Mime Jr. (Gen. 4)
- Chansey or Blissey with Luck Incense to get Happiny (Gen. 4)
- Snorlax with Full Incense to get Munchlax (Gen. 4)
- Mantine with Wave Incense to get Mantyke (Gen. 4)
After you get the egg from the Day-Care Man, you need to hatch the egg. Hop on your Bicycle, and go on a long ride somewhere, as the time an egg takes to hatch is based on the number of steps you take, so keep on doing this until the egg hatches. If you really want, you can go back and forth between areas to hatch your egg. Every Pokémon takes a different amount of steps to hatch. Some of the amounts of steps are:
|# of Steps||Pokémon|
|2,560||Azurill, Cleffa, Igglypuff, Pichu, Togepi|
|3,840||Caterpie, Corphish, Geodude, Hoothoot, Illumise, Ledyba, Lotad, Nincada, Pidgey, Poochyena, Rattata, Seedot, Sentret, Shroomish, Skitty, Slakoth, Spearow, Spinarak, Spinda, Surskit, Tailow, Volbeat, Wurmple, Zigzagoon, Zubat|
|5,120||Abra, Aipom, Baltoy, Barboach, Bellsprout, Bulbasaur, Cacnea, Carvanha, Charmander, Chikorita, Chinchou, Clamperl, Corsola, Cubone, Cyndaquil, Delibird, Diglett, Ditto, Doduo, Drowzee, Dunsparce, Ekans, Electrike, Exeggcute, Farfetch'd, Feebas, Gastly, Girafarig, Gligar, Goldeen, Grimer, Growlithe, Gulpin, Hoppip, Horsea, Houndour, Kangaskhan, Kecleon, Koffing, Krabby, Lickitung, Luvdisc, Machop, Magnemite, Makuhita, Mankey, Mareep, Mawile, Meditite, Meowth, Miltank, Minum, Mudkip, Murkrow, Natu, Nidoran♀, Nidoran♂, Nosepass, Numel, Oddish, Paras, Phanpy, Pineco, Plusle, Poliwag, Ponyta, Porygon, Psyduck, Qwilfish, Ralts, Remoraid, Rhyhorn, Roselia, Seel, Seviper, Shellder, Shuckle, Slowpoke, Slugma, Spheal, Spoink, Squirtle, Stantler, Staryu, Sudowoodo, Sunkern, Swablu, Swinub, Tangela, Tauros, Teddiursa, Tentacool, Torchic, Torkoal, Trapinch, Treecko, Voltorb, Vulpix, Whismer, Wingull, Wooper, Wynaut, Yanma, Zangoose|
|6,400||Absol, Castform, Chimecho, Duskull, Elekid, Heracross, Lunatone, Magby, Mantine, Misdreavus, Mr. Mime, Onix, Pinsir, Sableye, Sandshrew, Scyther, Shuppet, Skarmory, Smoochum, Solrock, Tropius, Tyrogue, Venonat|
|7,680||Anorith, Kabuto, Lileep, Omanyte|
|8,960||Aerodactyl, Aron, Eevee|
|10,240||Bagon, Beldum, Chansey, Dratini, Lapras, Larvitar, Relicanth, Snorlax, Wailmer|
Also, legendaries can be hatched from eggs via GameShark or Action Replay:
|# of Steps||Pokémon|
|30,720||Mew, Mewtwo, Celebi, Ho-oh, Lugia, Deoxys, Jirachi, Rayquaza, Groudon, Kyrogre, Latios, Latias|
|20,480||Moltres, Zapados, Articuno, Suicune, Entei, Raikou, Registeel, Regice, Regirock|
Eggs hatch into Pokémon at Level 5 in Generation II and III and at Level 1 in Generation IV,. You may notice by looking at the egg's status in your party that the Trainer Memo sometimes changes depending on how many steps you've taken – this can help determine how many more steps you must take before the egg will hatch. The type, OT, and IDNo values are all ???, but by using this Breeding Guide you should be able to find out what moves the baby Pokémon will have.
 Egg groups
All Pokémon belong to at least one group, but certain Pokémon fall into more than one group. Two Pokémon can only breed if they are in the same egg group. The list of egg groups are as follows:
- Mineral/ Rock
- Water A
- Water B
- Water C
Pokémon fall as follows into the groups:
|Monster||Unbreedable||Water A||Water B||Water C|