SynopsisThe preferred temperature of three Hawaiian coral-reef fishes -Acanthurus triostegus sandvicensis, Abudefduf abdominalis, and Chaetodon multicinctus -were determined in twochambered tanks that permitted the fish to regulate behaviorally tank temperature. Median selected temperatures over 12 h were as follows: adult C multicinctus, 24.0" C; juvenile C multicinctus, 27.0" C; adult Ab. abdominalis, 25.9" C; juvenile Ab. abdominalis, 30.2" C; adult AC. triostegus, 29.2" C; juvenile AC. triostegus, 29.3" C. Juvenile Ab. abdominalis selected significantly higher median temperatures than the adults. C multicinctus and juvenile Ab. abdominalis selected higher median temperatures during the day than at night.