Due to the lack of a specific marker for gonocytes from newborn rats, isolation of these cells has proven difficult and laborious. We have found a specific cell membrane marker, the Epithelial Cellular Adhesion Molecular (Ep-CAM) that can be used to isolate these cells using antibody directed cell sorting. 4 days post partum (dpp) rat testes were enzyme treated to attain a cell suspension, which was labelled with an antibody (GZ1) against Ep-CAM and tagged with a fluorescent probe. The labelled cell suspension was run through a FACS cell sorter, from which a gonocyte suspension of >85% purity was attained. The cells remained viable in culture and proliferated actively as determined by double labelling the cells with anti-HSP90alpha (a specific germ cell marker) and anti-BrdU antibodies (after BrdU incorporation). During culture, these cells formed chains of 2 to 4 cells and aggregates of proliferating germ cells were found after 8 days of culture.