Spermatogenesis is a complex process of cellular multiplication and differentiation, the regulation of which is only partially understood. This may be due; 1) to the redundancy of the mechanisms of local regulation; 2) to the ubiquitous character of those growth factors and cytokines present in the testis; 3) to the lack of long term culture systems allowing male germ cell development. We describe herein two culture systems associating Sertoli cells and germ cell in which part of the meiotic step can occur in vitro. In the first system, pachytene spermatocytes prepared by centrifugal elutriation are cultured on a layer of Sertoli cells. In the second system small fragments of seminiferous tubules are seeded in bicameral chambers. The cytological and immunocytochemical studies presented show that pachytene spermatocytes of stages IV-VI differentiate into spermatids of steps 1 to 5.