The reproductive cycle of the cockle Cerastoderma edule was studied by histological techniques and observation of changes in the condition index during three consecutive years in the Ría de Vigo (Northwest Iberian Peninsula). The onset of gametogenesis took place at the end of the summer (September to October), progressed throughout the winter, and the mature stage was finally reached in spring. The first spawning occurred in April and May and, after gonad restoration, another spawning episode took place in May and June. During the summer (July and August), most of the population showed signs of gonad exhaustion, although a less-intensive spawning event was observed at the end of summer and beginning of autumn. This second episode coincided with a phytoplankton bloom, which acted as a stimulus for spawning. Although a simple measure, the condition index proved to be a good indicator of the gonadal cycle, because it reflected adequately the reserve accumulation during gametogenesis, maximum maturity, and gamete emission. The useful information obtained from this study can be applied in shellfishery management.