Cleaning behaviour is reported for rock cook (Centrolabrus exoletus) in their natural habitat at Isla de las Palomas (Tarifa, Gibraltar Strait area). Behavioural sequences of cleaning are described, and the contents of 92 guts were examined. Field observations and food analysis indicate that the rock cook is a facultative cleaner. Both juveniles and adults cleaned throughout the whole year, especially to species of families Labridae, Pomacentridae, Sparidae and Serranidae. Diet consists primarily of free-living copepods and gnathiid isopod larvae (Gnathia sp.). Comparisons are made between rock cook and the most active cleaner in the Mediterranean, Symphodus (Crenilabrus) melanocercus.