Two ways to get the national dex!
Have over sixty Pokemon in your Pokedex and defeat the Elite Four. Return to Pallet Town and see the professor. He will give the National Dex to Gary and yourself. You can use it to see the data for all 386 Pokemon.
Use the following trick to get the National Pokedex before defeating the Elite 4. Pokemon Ruby or Sapphire and an already completed game of Fire Red or Leaf Green is required. Trade a Pokemon that does not appear in Fire Red or Leaf Green into the completed version. Then, use the wireless link to send the new Pokemon into the incomplete game.
Added by: Pravinj Apr 18th 2012, ID#13700