Bilateral ovarian-adrenal vein catheterization and androgen measurements in the efferent samples were utilized to directly assess glandular steroid release in 8 healthy volunteers with proven ovulatory cycles during the early follicular phase. Side effects did not occur in any of the women. Hormone levels were as follows (mean +/- SD; ng/ml) T: peripheral vein (PV) 0.36 +/- 0.16, ovarian veins (OV) 0.39 +/- 0.13, adrenal veins (AV) 0.85 +/- 0.63; dihydro-T (DHT): PV 0.25 +/- 0.09, OV 0.29 +/- 0.10, AV 0.93 +/- 0.65; delta 4-androstendione (A): PV 0.88 +/- 0.34, OV 1.82 +/- 1.04, AV 9.22 +/- 8.04; DHEA; PV 5.13 +/- 1.96, OV 6.73 +/- 2.69, AV 146.79 +/- 217.24; DS PV 1860 +/- 850, OV 1937 +/- 1039, AV 2567 +/- 1201; 17 alpha-hydroxyprogesterone (17P): PV 0.60 +/- 0.19, OV 1.46 +/- 1.64, AV 6.94 +/- 6.20; F: PV 170 +/- 50, OV 130 +/- 21, AV 788 +/- 1320; the bilateral differences of effluent levels were not significant. Glandular-peripheral vein steroid gradients served as semiquantitative estimates of momentary secretory activity; they were as follows (mean +/- SD; ng/ml) T: ovarian-peripheral vein gradient (OPG) 0.03 +/- 0.09, adrenal-peripheral vein gradient (APG) 0.48 +/- 0.57; DHT: OPG 0.05 +/- 0.05, APG 0.69 +/- 0.60; A: OPG 0.97 +/- 1.13, APG 8.33 +/- 7.86; DHEA: OPG 1.70 +/- 1.80, APG 141.80 +/- 216.60; DS: OPG 191 +/- 72, APG 706 +/- 824; 17P: OPG 0.87 +/- 1.67, APG 6.30 +/- 6.10; F: OPG 38 +/- 11, APG 610 +/- 1329. Gradient, analysis revealed that the ovaries produced significant quantities of A, DHEA and 17P, but no T, DHT or F between day 3-7 of the cycle; direct gonadal DS output was detected in 2 individuals. A significant OPG for DS was detected in two individuals possibly indicating its partially gonadal origin. The adrenals released larger amounts of A, DHEA and 17P than the ovaries at this stage (P less than 0.05); also, they consistently secreted T, DHT, DS and F.