Little is known about the role of ovarian nerves in the control of steroid secretion. We have examined the effect of sectioning the adrenergic superior ovarian nerve (SON) on the secretion of progesterone (P), and estradiol (E2) from the ovary. The steroids were measured in blood samples collected every 4 min from the ovarian vein in the proestrous and estrous phases of the rat estrous cycle. Upon section of the nerve at 1100 h of proestrus, secretion of both steroids dropped within 4 min and remained at about 50-60% of presection values for the rest of the sampling period. At 1600 h of proestrus, systemic plasma LH was elevated and P output was markedly increased. SON section produced a transient (8-min) decrease in P levels, but E2 concentrations remained depressed. Section of the SON during estrus failed to alter the output of either steroid. SON section did not alter blood flow. It is suggested that neural impulses, possibly adrenergic, which reach the ovary via the SON contribute to the maintenance of gonadotropin-supported secretion of ovarian steroids on the day of proestrus. The results are consistent with the view that, in addition to its hormonal regulation, the ovary is directly controlled by the central nervous system (CNS) through specific neural pathways.