On the basis of the semen analysis in 66 subjects, they were divided into six different groups: Group I consisted of 16 normal subjects with sperm counts of over 40 ${\times}10^6$/ml and motility of over 40 percent, Group II, 7 subjects with normal sperm counts, but motility of under 40 percent, Group III, 15 oligospermic patients with under 40 ${\times}10^6$/ml, Group IV 14 azoospermic patients, Group V, 10 patients with vasectomy and Group VI, 4 abnormal patients with 2 cases of hypoplastic testis, 1 case of Klinefelter's syndrome and 1 case of testis tumor. After seperation of semen into sperm and seminal plasma by centrifugation, the protein contents and the activities of hyaluronidase, ${\beta}$-N acetylglucosaminidase, ${\beta}$-glucuronidase, arylsulfatase, acrosin and azocoll proteinase in seminal plasma were measured. Vasectomy group has 30 percent less of total protein than normal group. For the comparison of enzyme activities of seminal plasma, it could be assumed that the enzymes in seminal plasma were not contaminated with the enzymes of spermatozoa by testing the enzymes of the seminal plasma from the vasectomy and azoospermic groups. It had been reported that hyaluronidase was only released from spermatozoa, however, the result obtained in this investigation showed that azoospermic and vasectomy group had high specific activities of hyaluronidase. The results indicated that hyaluronidase was not only from the testis but also from the male accessory sexual glands. Oligospermic group (Group III) showed the lowest total activity of hyaluronidase among them. The specific activities of ${\beta}$ -N-acetylglucosaminidase was high in oligospermic group (Group III) and low in vasectomy group (Group V). These results were contradictory with the pattern of hyaluronidase activities. This indicated that the spermatozoa which were stayed in epididymis would increase the activity of this enzyme. The specific activity of ${\beta}$ - glucuronidase was low in oligospermic and vasectomy groups. Group VI including testis tumor had remarkably high arylsulfatase activity. Arylsulfatase, a typical lysosomal enzyme, has been known to be released unusually large amounts from certain tumor cells. Arylsulfatase was also released with high activities from azoospermic and vascetomy group. This result indicated that this enzyme was also released from the sources other than testis. Acrosin, a proteolytic enzyme locating in the sperm acrosome, was not found throughout all the samples of seminal plasma. The activities of azocoll proteinase, a non-specific neutral proteinase was nearly identical in all the groups. This enzyme must have been released from the sources other than testis.