PIP: 55 patients under clomiphene treatment were studied during 149 cycles. In addition to the usual tests and controls, the authors made a basal temperature curve, took samples of cervical mucus and performed vaginal cytology tests, and calculated the average duration of the cycle. The cycle study based on the Sims Huhner test was also performed on 13 patients. Changes in the results of the tests were found to be related to the dosage and, above all, to the date on which treatment is started. Knowing the changes that occur in the cervical mucus and basal temperature, these 2 tests helped in detecting ovulation. Postcoital cervical sperm penetration improved 1 week after taking the last tablet. The duration of the menstrual cycle increased while taking the drug, and this prolongation of the cycle increased as the drug was administered at a later stage. With respect to vaginal cytology, it is necessary to know the changes that occur in order to interpret the findings correctly; vaginal cytology studies are unreliable in determining the occurrence and especially the probable date of ovulation.