In the present paper we investigate whether the adhesion that occurs in vitro between mouse fetal germ cells and follicle cells is accompanied by the establishment of cell coupling between the two cell types. The possible coupling between germ cells that spontaneously aggregate in culture has also been monitored. When germ cells, isolated from the gonads of 12.5-13.5-day-post coitum embryos, were loaded with 6-carboxyfluorescein diacetate and seeded onto follicle cell monolayers dye was transferred from the germ cells to the adjacent somatic cells within 2-3 h of culture. No dye transfer was observed when germ cells were seeded on fibroblast monolayers or between members of homotypic germ cell aggregates. These results indicate that, following cell to cell adhesion, fetal germ cells are able to establish heterocellular gap junctions with somatic cells of gonadal origin in culture.