Effects of a single s.c. injection of 1 or 5 mg/rat of CdCl2 on circulating steroids and fertility were studied over a period of 120 days in fertile male rats. Androgens and fertility returned to normal 120 days after 1 mg CdCl2, but males treated with 5 mg showed no to poor restoration of some of these parameters. The in vitro release of testosterone (T), 5.alpha.-dihydrotestosterone (5.alpha.-DHT) and androstenedione (.delta.4A) by the decapsulated testes from CdCl2 treated males was significantly reduced, whereas progesterone (.delta.4P) was accumulated in significantly higher amounts into the incubation medium. When testes from CdCl2 treated males were incubated in vitro with hCG, a dose and time dependent stimulation of steroidogenesis was evident. Since the testes regained the steroidogenic capacity, but the males remained sterile 120 days after 5 mg CdCl2 treatment, it appeared that CdCl2 induced a permanent damage to the germinal components of the testes.