The collagen content and collagenase activity were estimated in human ovarian interstitial tissue devoid of all visible follicles in menstruating, fertile as well as climacteric women. The mean total collagenase activity in ovarian specimens taken during both follicular (n = 10, 3.97 +/- 0.58 U/g wet weight, ww) and luteal phase (n = 10, 3.39 +/- 1.24 U/g ww) of the normal menstrual cycle along with total collagen concentration (184.8 +/- 41.0 vs. 194.4 +/- 30.5 micrograms/mg ww, respectively) did not differ. Total collagenase activity of climacteric gonads (n = 5, 1.55 +/- 0.71 U/g ww) was lower than in specimens collected during both follicular and luteal phase (p = 0.0002 and p = 0.017, respectively). About 23% of the total collagenase activity in follicular phase ovarian extracts and only about 1% in luteal phase ovarian preparations was found in the latent form. The percentage of latent collagenase in ovarian tissue during the follicular phase was negatively correlated with the day of the menstrual cycle (r = -0.93, p = 0.007). Extracellular matrix remodelling in the human ovary can be correlated with the functional status of the follicular unit.