The serum concentrations of cortisol, aldosterone, progesterone and catecholamines were determined 30 min, 1, 2, 4, 8, 24 and 48 h after application of single doses of titanocene dichloride (60 mg/kg) and of cisplatinum (10 mg/kg) to non-pregnant and to pregnant mice (treatment on day 10 of gestation). Whereas cisplatinum administration did not alter the serum content of these hormones, titanocene dichloride induced 5-6-fold increases in serum cortisol concentration of pregnant as well as of non-pregnant mice within 1-2 h after substance application. The serum levels of aldosterone, progesterone and catecholamines were not influenced by treatment with titanocene dichloride. It is supposed that the augmentation of cortisol in the serum is due to a rapid release of cortisol from the suprarenal glands after application of titanocene dichloride, thus mediating indirectly the induction of cleft palate in mice.