The game can be played against the computer or with another player. You have the option to have 1, 2 or 3 players in the field. As a pitcher, you use the joystick to throw the ball and to control its speed and curve. After the ball is hit, your control all your men (they all move together since they follow the orders of a single joystick) in the field to catch the ball. As a batter, you can control the position of the baseball bat with the joystick. If you consider that your runners would make it to the next base, you can press the controller button so they stop at their current base.
The rest of the rules are basically like real baseball. Each team has nine innings in a game. You are out after three strikes, your get to first base after four balls (balls that do not fly over Home) or if the pitcher hits you with a ball. In the field, you can put out a batter by catching his ball, then another runner by reaching his next base before him or simply by touching him between bases, thus completing a double play. The only way to accomplish a home run is by hitting the ball over second base without having it caught by the field players. You score a point for each runner that reaches Home base after each of the first three.