LDH-X, an isoenzyme of lactate dehydrogenase specific for germinal epithelium activity, was measured in the seminal plasma of infertile and fertile subjects. A total of 96 semen samples were classified into the following four groups: 1- men with proven fertility (n=27); 2- moderate oligozoospermic subjects (n=25): 3- severe oligozoospermic subjects (n=22): 4- azospermic subjects (n=22). LDH-X was analyzed quantitatively in semen. A good correlation was found between LDH-X activity and totol sperm count (r=0.686, P