Reproductive cycles of four species of limpets were determined using quantitative analyses of counts of eggs and weights of gonads. Montfortula rugosa has a breeding season extending for 8-9 months, but does not show marked peaks of reproductive activity. It spawns small numbers of eggs over a long period, and never has a very large gonad. Notoacmea petterdi has a very short spawning season in May or June. Prior to spawning the gonad may account for over half the wet weight of an individual. After spawning there is a long resting period, after which the size of the gonad and the number and proportion of mature eggs increases gradually over the next 7-8 months. Patelloida alticostata and P. latistrigata have strategies which are intermediate between the other two species. Spawning may occur over a 4-6 month period during which time there are two peaks of spawning activity. The production of mature oocytes recommences soon after spawning has ceased in July, and the gonad rapidly increases in size during the following 4 months. Estimates of fecundity are given for the three species of acmaeid limpet. In these species, fecundity increases with increasing size; yet individuals are capable of producing and spawning mature eggs at the end of their first year on the shore. The adaptive significance of such a strategy is discussed.