The zinc concentration in seminal plasma from 98 infertile male patients and 8 fertile males was measured. The zinc concentration of the seminal plasma in azoospermic and oligoasthenozoospermic patients was significantly lower than that in the other groups (each, p<0.05 ). The seminal plasma zinc concentration in asthenozoospermic males was significantly higher than that in any other group (p<0.05). There was a positive correlation of zinc concentration with sperm concentration (r=0.33, p<0.05) and with sperm motility (r=0.22, p<0.05), while there was no correlation with sperm morphology. A correlation between zinc concentration and plasma testosterone concentration was observed (r=0.24, p<0.05). It is concluded that excessively high zinc concentration is apparently related to defective motility in asthenozoospermic patients, even though adequate seminal plasma content of the element is required for normal sperm function.