Mugil cephalus Linnaeus is a grey mullet of commercial importance in Porto Novo. Maturity and spawning of this mullet was studied by observations on the gonads collected from December 1977 to November 1978. Males were found to mature earlier than females. High G.S.l. values were noted from September to April. Different stages of maturity were noted from ova diameter studies as also the spawning season and the breeding periodicity. Fishes were found to spawn only once during the breeding season which seems to be an extended period from September to April, with a peak during October to January.