Expedition Base Set was the third base set to be released in English-language territories after Base Set and Base Set 2, and was also the largest set ever released at the time (a title previously held by Base Set 2, at 130 cards). Many aspects of the set differed greatly from previous expansions, most noticeably the card layout, of which the left and bottom borders had been increased in size due to the newly-included Dot Code technology for use with the Nintendo e-Reader. By using the device, players were able to view Pokédex data about the Pokémon, play a minigame, play various tunes in a Melody Box, or activate a special attack for that Pokémon. These special attacks were not legal for use in tournament play as few competitors used e-Readers. As well as this, in the Unlimited Format used by Pokémon Organized Play, electronic devices such as the e-Reader are not allowed on the table.
The new card design also meant that Pokémon cards lacked Pokédex data and flavor text (Length, Weight, Level and Pokédex entry, information which is stored in the dot code along the bottom of the card), information which would not be seen on cards again for four years with the release of Diamond & Pearl. This absence, in the Unlimited Format, caused (and still causes) problems when using the Blaine's Quiz #1 Trainer card. Lack of level also meant that each Pokémon card included a unique ID number in order for the e-Reader to distinguish each card with the same name in a way other than by level.
Expedition also introduced a long-term game mechanic, one of the most important in gameplay: the division of Pokémon Powers into Poké-Powers and Poké-Bodies. Poké-Powers required activation to use, whereas Poké-Bodies were always active unless blocked by a specific card. It was only after the introduction of Abilities in Pokémon Ruby and Sapphire that the two separate types of Pokémon Powers (mainly Poké-Bodies) became considerably more useful and important.
Expedition could have been released in May 2002; however, it was delayed until August to ensure the e-Reader was released before the set. Further issues delayed it again until September. It was further delayed in Europe in order for the e-Reader to be released before it; however, the e-Reader did not see release in Europe, and the set was eventually released in April 2003.
- Because of the extra licensing fees Wizards had to pay to use Dot-Code technology, the pack size was reduced from 11 to 9; which remained the same for almost five years, even though the Dot-Code technology was dropped in 2004. The pack size would eventually increase to 10 with the release of Diamond & Pearl. Collectors could also find one reverse-Holofoil in every pack, meaning each pack contained:
- 5 Common cards
- 2 Uncommon cards
- 1 Reverse-holofoil card
- 1 Non-holofoil or holofoil rare card
- While it was thought Wizards were up to their old tradition of duplicating the rare cards in this set, it was actually MediaFactory this time; Wizards simply translated the set. The reason for this was that some rare cards had Dot-Code data, therefore they made non-holofoil versions with the data and holofoil versions without. This avoided potentially damaging sought-after rare cards when swiped through the e-Reader.
- Expedition was the first set Wizards produced that didn't have a 1st Edition print run.
- Expedition once again featured Reverse-holofoil cards, but the design was changed from the "wheel" treatment (which was reminiscent of European fake holofoil designs) to a plain "refractor" design. They are more "official" looking than the ones found in Legendary Collection. One problem brought to Wizard's attention was that both the holofoil and non-holofoil rare cards had identical reverse-holofoil counterparts (apart from the card number). Wizards rectified this in Aquapolis by numbering the holofoil cards differently and not producing reverse-holofoil for them.
- Box toppers once again appeared in this set. Like Legendary Collection, they are jumbo cards (therefore not tournament legal). Unlike Legendary Collection and the EX series, the box toppers were part of a sub-set (the cards numbered ##/12). The first 4 appeared in this set, the other 8 were released in Aquapolis and Skyridge respectively.
- This set was previously known as New Dimension, but since its initials were ND (the same as Neo Discovery and Neo Destiny), the name was changed.