The benthic phases of the life cycles of two populations of the polychaete Pereinereis cultrifera from the Bay of Algiers were investigated using field surveys. We found no differences in the life cycle of the two populations. In the Bay of Algiers, P. cultrifera reproduces without epitokal modifications. The lifespan of the species probably does not exceed two years. The reproductive period spans most of the year but is more intense in spring from March to May when the sea-water temperature starts rising. A few mature individuals were collected at the end of summer and in winter. The oocytes take 9 to 12 months to mature and their diameter at maturity is approximately 200 µm.