The sedentary polychaete Scolelepis squamata (Müller, 1868) has a wide geographical distribution, but its popu- lation dynamics is less known. This species is relatively abundant at Skhirat beach on the Moroccan Atlantic coast where its population dynamics was studied between December 1985 and March 1988 in terms of abundance, distribution on the shore, sexual maturation, recruitment period, growth and life span. The mean density ranged from 130 to 2800 ind.m-2 over the year according to the periods and successful of spawning and recruitment. Sexual maturation, which covered over 10 months of the year, began at the end of winter, reached a maximum in April-June and ended in autumn. The population exhibited a demographic strategy which included four recruitment periods per year, the summer recruitments were more important than those in spring and autumn. Prostomium growth was irregular and varied between 0.08 and 0.21 mm per month. The average life span was estimated at one year for individuals recruited in summer. Mean annual biomass was 5.57 g.m-2, mean annual production was 11.28 g.m-2.y-1 and mean P/B ratio was 2.03 y-1.