Street Fighter II follows several of the conventions and rules already established by its original 1987 predecessor. The player engages opponents in one-on-one close quarter combat in a series of best-two-out-of-three matches. The objective of each round is to deplete the opponent's vitality before the timer runs out. If both opponents knock each other out at the same time or the timer runs out with both fighters having an equal amount of vitality left, then a "double KO" or "draw game" is declared and additional rounds will be played until sudden death. In the first Street Fighter II, a match could last up to ten rounds if there was no clear winner; this was reduced to four rounds in Champion Edition and onward. If there is no clear winner by the end of the final round, then either the computer-controlled opponent will win by default in a single-player match or both fighters will lose in a 2-player match.
After every third match in the single player mode, the player will participate in a "Bonus stage minigame" for additional points. The bonus games includes (in order) a car-breaking event similar to another bonus round featured in Final Fight; a barrel breaking bonus game where the barrels are dropped off from a conveyor belt above the player; and a drum-breaking bonus game where drums are flammable and piled over each other. The bonus games were removed from the arcade version of Super Street Fighter II Turbo (although they are featured in the Game Boy Advance version).
Street Fighter II differs from its predecessor due to the selection of multiple playable characters, each with their distinct fighting styles and special moves. Unintentionally, a "bug" in the game's code enabled the player to "cancel" during the animation of some moves by performing another move, allowing for a combination of several basic and special moves. The "combo" system all fighting games would subsequently use as standard was, in fact, entirely accidental. Both of these features would be expanded upon in subsequent installments.