Ovarian fluid, milt and surfaces of egg collected from adult rainbow trout were examined for the presence of the causative agent of RTFS Cytophaga psychrophila. The bacterium was culturable from ovarian fluid from 2 of the 15 henfish tested, but no isolation was possible from milt. C. psychrophila was detected from the egg surface 14 days after fertilisation. Pseudomonas sp., and Cytophaga sp. predominated on the egg surface with bacterial numbers increasing with incubation time.