The hormonal changes in maternal serum during parturition induced by amniotomy and oxytocin (OXY) infusion or oral prostaglandin E2 (PGE2) medication have been compared in 68 patients (33 women in the PGE2 group, 35 in the oxytocin group). The effect of PGE2 differed from that of oxytocin. Thus the prostaglandin elicited increases in total estriol (p < 0.001) and decreases in prolactin (p < 0.01), TSH (p < 0.05) and HPL (p < 0.05) from the basal level to that immediately before parturition. Maternal serum cortisol levels rose to the same extent in both treatment groups (p < 0.001). The significant (p < 0.05) increase occurred earlier among women receiving PGE2 (two hours into therapy), even though labor pain was experienced later in this group. The serum estriol elevation in these patients was significant three hours after start of therapy (p < 0.05). A similar time course was noted for the decrease of serum prolactin in PGE2 treated patients. The drop in maternal serum levels of HPL and TSH in the PGE2 group was significant only immediately prior to partus. Neither PGE2 nor oxytocin induced changes in maternal serum levels of HCG or alpha-fetoprotein or estradiol. Oxytocin but not PGE2 lead to a decrease in maternal serum progesterone concentrations; this was significant (p < 0.05--p < 0.01) only late in labor. Mixed umbilical serum levels of the hormones mentioned above were the same regardless of method of induction. Hence the increased maternal estriol concentrations during PGE2 treatment were not reflected in fetal blood. It is suggested that increases in maternal estriol levels during PGE2 medication are due to effects on the maternal enterohepatic circulation rather than on the fetoplacental unit. Irrespective of maternal treatment umbilical serum from female newborns contained statistically higher (p < 0.05) levels of estradiol and HCG than serum from male children.