A roulette wheel (1) has a ball detector (9a, 9b, 9c) to detect the ball as the ball travels round the rim (3) of the roulette wheel and a drop determiner (21) to determine, for each of a number of games of roulette, the region of the rim from which the ball fell from the rim. Data representing, for a number of games, the region of the rim from which the ball fell from the rim may then be stored for later analysis or may be directly analysed to determine any drop zone bias. The ball detector may be a number of ball detecting elements (9a, 9b, 9c) spaced apart around the rim (3) of the roulette wheel for each providing a ball detection signal as the ball travels through a corresponding region (R1, R2 and R3) of the rim and the drop detector (21) may determine the region of the rim from which the ball fell from the rim by determining the detecting element passed last by the ball.