The diurnal, nonreproductive emergence of green turtles Chelonia mydas in Galapagos apparently occurs throughout the year on several islands. Turtles on beaches have cloacal temperatures that exceed temperatures of adjacent coastal waters. Basking turtles are predominately females. We hypothesize that females bask to accelerate digestion and fat build-up, necessary antecedents to egg production in reproductive periods. Basking turtles show a trend to clump among available beaches. Such behavior may be a response to microclimatic differences between beaches, although such differences were not apparent to us. The occurrence of thermoregulatory behavior in marine turtles in Galapagos may be a response to the cool waters of the Humboldt Current.