Seasonal variations in reproductive cycle of Spisula solida were studied between June 1995 and June 1996 at a site off Vilamoura, southern Portugal. Sex ratio was found to be in favour of males. Both males and females showed a synchronism in gonadal development and spawning. Gametogenic activity started with decreasing temperature at the beginning of autumn. The onset of spawning took place in February when the seawater temperature began to increase. Spawning ended in May. It is possible that the white clam does not spawn at a definite temperature, rather responding to the increase in seawater temperature. Between June and September, the specimens were found to be in the resting stage and the condition index increased, probably due to the accumulation of reserves. Spisula solida reached maturity during the first year of life.