Among 670 infertile men, 72 were diagnosed as pyospermia according to our criteria. i.e., WBC greater than or equal to 10/hpf semen. The sperm motile efficiency index (SMEI) which indicates the rate of progressively motile sperms, was significantly low in pyospermic group compared with that of non-pyospermic men (WBC less than 5/hpf semen). From the result of split ejaculation, a major cause of pyospermia was supposed to be chronic prostatitis. The SMEI was decreased immediately after addition of the neutrophils and granulocyte elastase to semen. The mean value of granulocyte elastase in pyospermic group was 2859.6 micrograms/L, whereas that of non-pyospermic men was 131.6 micrograms/L. In summary, granulocyte elastase in seminal plasma may be a cause of inhibition of sperm motility in pyospermic state.