Twenty-eight Pacific pilot whales (Globicephala scammoni) swam ashore on San Clemente Island off southern California on 8 January 1971. Investigation of the stranding led to collection of information on the bacteriology, reproductive tissue histopathology, liver mercury and DDE contents, and herd statistics of the species. These data together with the knowledge that squid were spawning just offshore and the meteorological conditions at the time led the authors to conclude that the stranding was a natural event precipitated by these optimal biological, beach, and tide conditions.