The authors began a statistical study on a file group of 9384 records of semen analyses and anamnestic data (P-1). From this file, they selected a group of 5191 patients having undergone analysis at least one time (P-2) and a file of 850 patients having undergone analysis at least three times (P-3). Finally a new group, derived from P-3, of 203 patients followed by their medical team was created (P-4). Two control groups-composed of 20 sperm-bank donors (DON) and 740 prevasectomy subjects (VAS)-were also created. Frequency distributions and cluster analyses were carried out. The multivariate statistical analysis allows a distinction to be made between fertile and infertile subjects regarding a patient's clinical condition. The most discriminating parameters appear to be sperm concentration and, above all, forward motility and sperm morphology.