The time course stability of urinary female reproductive hormones under different conditions was studied. Urine samples collected from healthy women 33 to 45 years of age and stored for various amounts of time at different temperatures were analyzed for luteinizing hormone (LH), follicle stimulating hormone (FSH), estrone-3-glucuronide (EG), pregnanediol-3-glucuronide (PG), and creatinine. The activities of FSH, EG, and creatinine decreased more rapidly over 2 weeks at 25 and 37 degrees-C compared with 4 degrees. Little to no activity was lost following storage of the hormones at 4 degrees. The addition of sodium-azide, thymol, boric- acid, or thimerosal did not significantly affect hormone activity. Following storage for 24 weeks at -80 degrees, activity ranged from 69.0% to 106.3%. The addition of glycerol and bovine serum albumin improved stability with activity ranging from 91.1% to 106.3%. Stability was unaffected by sodium-azide or boric-acid. The authors conclude that these results can be used to improve storage of urinary hormones for use in epidemiologic studies.