A postcoital examination made after the use of the contraceptive Experimental Jelly "P" by 200 women was used to evaluate the longevity of spermatozao, and the value of the experimental jelly as a contraceptive. 158 of the women (95% black, 5% white) returned to the clinic for 1 or more visits over a period of 3-18 months. 37 patients had used other contraceptive measures previously. After a medical history and physical examination each patient was instructed in the proper use of the method. With an applicator, 5 cc of the jelly was to be placed in the upper vagina, close to the cervix, 5-10 minutes prior to coitus. A douche could be taken after a minimum of 6 hours. Whenever possible, the examination was made a few hours after coitus. Vaginal and cervical contents were examined for spermatozoa, leukocytes, trichomonads, monilia, and spinnbarkeit of mucus. Occasionally uterine samples were aspirated. At the phase of maximum spinnbarkeit the longevity of spermatozoa was optimal and the need for an active contraceptive greatest. Therefore, the efficacy of the Experimental Jelly P at this time and at the estimated menstrual calendar ovulation time was especially noted. A total of 289 postcoital tests were done on the 158 patients at 2-72 hours postcoitus. Of the 289 tests 173 (59.8%) revealted no spermatozoa, 110 (38.1%) showed nonmotile sperm, and motile sperm were found in only 6 (2.1%). Effect of the jelly on cervical mucus did not penetrate to the endocervix. 30 pregnancies occurred. However, 23 of these women admitted to incorrect or inconstant use of the method. 83 women were followed for 3-18 months. 18 of them became pregnant but in only 7 instances was failure of the correctly used method thought to be the reason. The rate for jelly failure was 17.46 pregnancies per 100 woman-years of exposure. The reduction in fertility was estimated to be 83.17%. Of side effects, 49 patients complained of local burning. In some instances both partners complained. 12 of these women were found to have monilial vaginitis. The burning ceased when this condition was treated. Many complained of the messiness of the method. The postcoital test is considered an accurate method in the evaluation of spermicidal preparations used as contraceptives.