Velocities achieved by the upper punch of an eccentric tablet press during compaction have been compared with those predicted by equations describing the movement of the punch in an empty die. Up to the point of maximum punch penetration, actual speeds are invariably less than the predicted speed, the magnitude of the deceleration being determined by the machine speed and applied force. As the punch withdraws from the die, its speed can exceed that predicted on theoretical grounds, due to the elastic expansion of the tablet assisting punch ejection.