Sonicated Neoparamoeba spp. (Nspp) did not affect the in vitro respiratory burst response of leucocytes isolated from Atlantic salmon Salmo salar, rainbow trout Oncorhynchus mykiss and chinook salmon Oncorhynchus tshawytscha anterior kidneys (P > 0.05). Atlantic salmon and chinook salmon leucocytes pre-incubated with the parasites, however, responded to phorbol myristate acetate (PMA) stimulation with a greater response compared to cells incubated with PMA on its own (P < 0.05). Sonicated Nspp was not chemo-attractive for anterior kidney leucocytes isolated from all three fish species. ?? 2006 The Fisheries Society of the British Isles.