The sperm penetration test introduced by Kremer was studied, using cervical mucus as the test medium and human semen samples with varying properties. The spermatozoa from semen samples of good quality penetrated rapidly, to more than 30 mm within one hour. Spermatozoa from semen samples of poor quality penetrated slowly and a maximum penetration of less than 20 mm was noted. Capillary tube size, incubation temperature, and the amount of mucus protruding from the capillary tube, had no appreciable influence on the results. Reproducibility was good. Storage of the cervical mucus at + 4°C or ‐ 20°C for 3 weeks did not influence its suitability as a test medium. The test is easy to perform and well suited for routine semen analysis.