Our knowledge of the biology of fish gametes is still limited. Up to now research was short-term, aiming at solving practical questions connected with gamete storage and artificial insemination. More information on gamete biology is now available and has been summarized in this minireview.In vivo storage of gametes in the genital tract after ovulation or spermiation may be influenced by the osmotic environmentvia changes in the ionic composition of the companion fluid. There is great inter-individual variability in gamete survival bothin vivo andin vitro. Mechanisms involved in the initiation of trout sperm motility have been analysed; after dilution in water or NaCl solution (125 mM) at pH > 7, Ca(++) entry due to changes in membrane potential have been observed. The involvement of cAMP and protein phosphorylation has been reported. The morphological, physical and biochemical changes in eggs that have been studied after fertilization and the corticol reaction lead to a better understanding of the mechanisms of polyspermy blockage.