Urinary glycosaminoglycans (GAGs) content showed a characteristic pattern of fluctuation during normal and hormonally induced cycles with a distinct peak at ovulation. This peak of maximal GAGs concentration (106.7 +/- 46.2 micrograms/mL in urine) was centered according to the day of the midcycle LH surge, which serves as the reference point, designated day 0. All cycles are presumed to be ovulatory on the basis of biphasic BBT nadir, ultrasonographic studies, and progesterone assays (greater than 5 ng/mL of serum) during the secretory phase. In hormonally induced menstrual cycles, a noticeable increase in GAGs concentration (70%) was observed. This indirect evidence suggests a possible correlation between GAGs content and hormonal effect. All types of GAGs, with the exception of heparin, have been found in urine, chondroitin sulfate C being the major component at time of ovulation. These results strongly suggest that urinary GAGs determination is a precise method for ovulation detection.