Crab-eating macaques on Angaur are an exotic fauna introduced to the island in the early 1900’s. The present population of 480-600 animals reportedly are descendents of a pair of monkeys brought to the island by German phosphate miners. During a 10-Week period, June to August, 1973, we spent a total of 253:30 hours in the field locating and studying monkeys. Of this total, 75:30 hours are direct observation time. This article discusses aspects of the ecology, social behavior, and problems of adaptation of the Angaur crab-eating macaques.