Two cases of male infertility due to pathological dilatation of seminal duct end are reported. One patient was 33 years old. He was diagnosed with azoospermia by semen analysis. The cystic wall of the seminal duct end was incised by a cold knife on the urethral scope. After the operation, 100,000-500,000/ml sperms were found in his semen. The other patient was 31 years old. He was diagnosed with severe oligoasthenozoospermia. He was operated on in a similar operation. After operation, the findings of his semen analysis improved exceedingly, and his wife became pregnant.