Base Set (Japanese: 拡張パックExpansion Pack) is the name given to the original core release of cards and Theme Decks for the Pokémon Trading Card Game. It was released in Japan on October 20, 1996, and in the United States on January 9, 1999.
An advertisement for the original Japanese release
While the expansion began the TCG in the United States officially in January of 1999, many stores were initially reluctant to sell the game. As a result, it did not see a widespread release until March or April of that year.
The 1st Edition print run sold extremely quickly, making first edition Base Set cards some of the most sought-after of all of the early TCG expansions.
All cards in the first few print runs (both first edition and unlimited) were printed with thinner HP and attack text and without drop shadows for the illustration window. These are commonly known as "shadowless cards" and are more valuable than later runs.
This expansion was replaced by Base Set 2 on its release, as by that point Base Set had been out of print for some time.
Several final form Pokémon were left out of this set despite their pre-evolved forms appearing, such as Dragonite, Dodrio, Gengar, Pidgeot, Sandslash, Butterfree and Hypno. These cards were later released in Jungle and Fossil.
Changes between the Japanese and international release
In TCG expansions up until Pokémon VS, the Japanese cards did not have a numbering system, and so the only number featured on the Japanese cards is the Pokémon's National Pokédex number.
The English cards adopted a system based on ordering the cards alphabetically and by descending rarity (rare-holo, rare, uncommon, common) and class of card (Pokémon, Trainer, Energy). This ordering remained in place until the release of Black & White. The Japanese set is ordered by type (Grass, Fire, Water, Lightning, Psychic, Fighting, Colorless), National Pokédex number, and ascending rarity (rare and rare-holo counting the same). This ordering remained in place until e-Card 2.