The ascidian populations of the eight Channel Islands, as well as three islets, the Cortez Bank and the Coronado Islands were surveyed. Thirty- eight species were found offshore compared to the 48 identified species which have been found above a depth of 60 m in southern California. It was observed that viviparous ascidians are specifically more abundant than oviparous ascidians on the Channel Islands and the possible significance of this mode of reproduction is discussed as an explanation for their local distribution. The habitat preference of southern California ascidians is presented. Nine species of ascidians of unresolved identification are compared to the most closely related, described North American species.