Levels of unconjugated oestradiol-17 beta (E2) and testosterone (T) and total oestriol (E3) were measured hourly to 6 h after intra-amniotic (i.a.) (100--200 mg) or intravenous (i.v.) (100 mg) injection of dehydroepiandrosterone sulphate (DHEA-S) in a series of twenty-six women with mid-trimester abortion. Amniotic fluid E2 and T levels were elevated significantly 1--6 h after the i.a. injection of DHEA-S, while the E3 level in amniotic fluid did not change. The i.a. administration also induced significant rises in serum E2 and T levels between 1 and 6 h and in the serum E3 level between 2--6 h. The i.v. injection of DHEA-S was accompanied by significantly elevated serum levels of E2 and T, while the E3 concentration remained unchanged. It appears that following maternal i.v. administration or an amniotic fluid injection, DHEA-S is rapidly converted to E2 and T, and these accumulate in both the maternal circulation and the amniotic fluid. E3, however, is formed only after i.a. administration of DHEA-S, and is selectively transported to the maternal blood.