The pressure wave produced by the collapse of an electrically generated spherical cavity (∼1 cm in radius) in water was measured by means of a small electroacoustic hydrophone (116 in.in diameter) at a distance of 50 cm. The pressure was found to increase as the bubble collapsed according to thet−4/5(time) law in the interval corresponding to subsonic flow. The pressure then suddenly jumped to a higher value and rapidly decayed to zero. This rapid increase in pressure is assumed to be a shock wave. Using Gilmore's theory for the collapse of the cavity and finite amplitude‐wave theory for the pressure wave, we find that the value of the pressure‐amplitude characteristic at the shock front corresponds to a cavity‐wall velocity approximately equal to the velocity of sound. Since the shock wave has been attenuated, the peak wall velocity must be greater than this value.