The analysis of 751 postcoital tests performed in patients consulting the infertility clinic of the Department of Obstetrics and Gynecology, University of Cologne, allows the following diagnostic and prognostic conclusions: 1. In case motile spermatozoa are present in the cervical mucus, the assumption can be made that adaequate insemination takes place. 2. The postcoital test and the simultaneous examination of the cervix factors offer themselves for the assessment of the estrogenic status during the normal cycle or after stimulation with clomiphene, HMG-HCG or estrogen. 3. The timing of the postcoital test itself results in a remarkable increase in pregnancy rates. 4. The pregnancy rates are higher when higher numbers of motile sperms are found in the cervical mucus. 5. Negative or doubtful postcoital tests do not rule out the possibility of pregnancy. 6. The postcoital test provides some information about the number of spermatozoa, their progressive motility, their morphology and about the interaction of spermatozoa with the cervical mucus. However, the postcoital test cannot replace a complete semen analysis.