The premoult stages of Carcinus maenas (L.) megalopae were described from laboratory-reared larvae. Characterization of the premoult stage sequence was based upon a time sequence of morphological modifications of the distal segment of the second maxilliped, the uropod, and the telson. An intermoult plus seven premoult stages were identified, following a sequence of morphological modifications similar to the one described in previous studies of brachyuran decapods. The later premoult stages D₃ and D₄ mentioned by Drach were not observed, possibly owing to both the low calcification of the megalopae cuticle and the short duration of these moult stages. The knowledge of the time series of moult events will assist in the evaluation of the development state and competence of megalopae throughout the several phases of dispersal and recruitment, based on the observation of their morphological characters.