Effects of nonapeptide hormones and of some of their chemical analogues on progesterone and testosterone production by culture of porcine granulosa cells have been investigated. Oxytocin (0,01-10 IU/ml), arginine-8-vasopressin (0,01-10-mu-g/ml), arginine-8-vasotocin (0,01-10-mu-g/ml) and, in a lesser degree, 2-0-methyl-tyrosine (deamino-1-karba) - oxytocin (0,01-10-mu-g/ml, but no 1-deamino-8-vasopressin (0,01-10-mu-g/ml) stimulated a progesterone surge. Testosterone production was significantly stimulated by oxytocin and inhibited by vasopressin or vasotocin additions. 2-0-methyl-tyrosine (deamino-1-karba) - oxytocin or 1-deamino-8-vasopressin had little or no effect on testosterone secretion. The present results suggest the existence of a direct influence of nonapeptide hormones on porcine ovarian progestagen and androgen production.