Inmature individuals of Ruditapes decussatus, collected from the Galician coast (Spain), were maintained in a laboratory open-flow seawater system over a 76-day period at a temperature of 18-20ºC and fed with Isochrysis galbana clone T-ISO. A histological study of gonad development was performed in subsamples of clams collected every 15 days. Although this species is considered strictly gonochoristic, two individuals displayed hermaphroditism in which both male and female gametes were present. It is suggested that these are cases of consecutive hermaphroditism.