Anaesthesia may depress the immune system in mammals, but there is no available information on this topic in fish. In the present work, four anaesthetics that are used in aquaculture, MS222 (0 19 mM), benzocaine (0.21 mM), 2-phenoxyethanol (16 mM) and quinaldine sulphate (0.083 mM), were tested in order to observe their effects on the gilthead seabream (Sparus aurata L.) innate immune system. The results showed that the four anaesthetics produced increased blood glucose levels after an hour. In addition, benzocaine and 2-phenoxyethanol depressed complement activity and phagocytosis, while MS222 and quinaldine sulphate did not. Some anaesthesia is a common practice in aquaculture, the data obtained should be taken into account to avoid possible immunodepression in farmed fish.