In the semen of the two bulls, abnormal structures, which were not identified with phase-contrast and dark-field microscopy, were observed. These samples were fixed, embedded in the plastic blocks and sectioned for examining with T.E.M. It was understood that the objects in the first sample were abnormal spermatozoa which have both head and tail anomalies. The objects in the second sample were not abnormal spermatozoa. They were leukocytes which infiltrated into the semen.