Zinc is an essential micronutrient for spermatogenesis and normal sperm function. However, the correlation of zinc level in seminal plasma and the results of semen analysis is controversial. This study aimed to evaluate zinc levels in seminal plasma of infertile men. One hundred thirty five left-over semen of infertile men collected from the Reproductive Biology Unit, Department of Obsterics and Gynecology, Faculty of Medicine, KKU were analyzed for semen analysis. The seminal plasma was then classified into 2 groups according to its results of semen analysis. Normal group was named normozoospermia (n = 61). The samples classified as oligospermia, asthenozoospermia, oligoasthenozoospermia, and azoospermia were included in abnormal group (n = 74). They were used for zinc determination by atomic absorption spectrophotometer. Zinc levels of normal and abnormal group were 14.21 mg% and 14.72 mg% , respectively. Mean values of zinc level in two groups were significantly different (P < 0.001) with 95 % CI of 11.75-16.68 mg% for normal group, and of 12.64-16.81 mg% for abnormal group. The results implied that determination of zinc level in seminal plasma of infertile men might not be very useful due to a miniscule difference mean value of this ion in both groups. Further study of zinc contents should be investigated in subgroup of semen analysis, or in comparing of fertile and infertile men.