Objective: To quantify nerve fibers and mast cells in human ovaries at different functional stages.Design: Retrospective study.Setting: Research laboratory of the university.Specimen(s): 8 human ovaries in the follicular (cyclic) phase, 7 polycystic ovaries, and postmenopausal ovaries with (n=5) or without (n=7) hyperthecosis.Main Outcome Measure(s): Single- and double immunohistology for the S100 antigen in glial cells of autonomic nerve fibers, for chymase and tryptase in mast cells, and for the common leukocyte antigen on leukocytes. Histometric evaluation was also performed.Intervention(s): None.Result(s): Polycystic ovaries contained significantly more S100-positive nerve fibers in the corticomedullary region than did cyclic ovaries (mean +/- SD per 2-mm 2 area, 476 +/- 136 and 224 +/- 133; P<.01). Postmenopausal ovaries with or without hyperthecosis had the highest density of nerve fibers. In cyclic and polycystic ovaries, more tryptase-positive mast cells than chymase-positive mast cells were found in the interstitial cortex and the medulla. In cyclic ovaries, areas with a moderate density of nerve fibers contained many mast cells. Hence, with increasing nerve fiber density in polycystic ovaries, the number of mast cells decreased strikingly compared with cyclic ovaries (p<.001). Almost no mast cells were seen in postmenopausal ovaries with and without hyperthecosis. The number of leukocyte antigen-positive leukocytes was similar in all groups.Conclusion(s): The high density of nerve fibers in polycystic and postmenopausal ovaries, together with a conspicuous decrease in mast cells, indicates altered neuroimmune communication.