During the normal menstrual cycle the volume of cervicovaginal fluid (CVF), as determined by the patient at home using a simple volumetric aspirating pipette, increases significantly over several days prior to the luteinizing hormone (LH) surge and decreases characteristically shortly after ovulation. The present study was undertaken to test the hypothesis that self-determined measurements of CVF volume would correlate positively with serum estradiol (E2)levels and with total follicular volume (TFV) in cycles stimulated with exogenous gonadotropins. Consequently, 20 infertility patients, undergoing human menopausal gonadotropin (hMG)-stimulated cycles, were asked to measure daily CVF. Routine serum E2determinations and vaginal follicular ultrasound studies were performed up to and including the day of human chorionic gonadotropin (hCG) administration (designated day 0). The mean daily CVF volume (±SD) increased from 0.1 ± 0.01 ml on day −6 to 0.7 ± 0.40 ml on day — 1 and then decreased to 0.6 ± 0.40 ml on day 0. On day 0, 7 of 20 cycles (35%) demonstrated a decrease in CVF, which ranged from 0.1 to 1.0 ml (mean, 0.42 ml). The mean daily CVF correlated positively (correlation coefficient = r) with the mean daily serum E2 (r = 0.89) and with the mean daily TFV (r =0.88). The mean daily correlation of TFV for E2 was r =0.98. The correlation between CVF and E2of individuals ranged from r =0.38 to r =0.99 and the correlation between CVF and TFV ranged from r =0.12 to r =1.0, while the individual correlations ofE2 to TFV ranged from r =0.60 to r =0.99. These early data suggest that, although mean daily levels of CVF increase positively over time, individual CVF levels are not sensitive enough, alone, to replace the traditional methods of monitoring hMG-stimulated cycles.