The ball size for table tennis was recently changed in the revision made to the international rules by the ITTF (International Table Tennis Federation), and the new ball has been in use for official games since October 2000. The new rules stipulate that the diameter of the ball should now be 40mm (an increase from 38mm), and the weight of the ball should be 2.7g (an increase from 2.5g). It is estimated that the style of play and game tactics will change to some extent as a result of the new ball. The purpose of this study was to compare the hitting properties of the new ball in comparison with the old one, in order to clarify the influence on play. The reduction ratio of ball speed from the shooting point to the receiving point was calculated using a ball-shooting machine and a speed measurement system. Initial velocities and ball spins were calculated using a golf-swing robot and a high-speed video camera system. The robot hit the balls with different hitting speeds and hitting angles by a racket attached to the robot arm. An all-around wooden bat pasted with a reverse-soft rubber sheet was used. Average rally times for the two kinds of ball were measured, and three kinds of basic shot-drive, chop and serve-were made in the rallies by skilled payers. The following results were obtained: (1) The initial speed of the new ball was 1-2% less, and the ball spin was 5-20% less than for the old ball. (2) No difference in the speed reduction ratio was observed between the new ball and the old one. (3) The average rally time for the new ball was 2-4% longer than for the old ball for drive and chop shots.