Spermatozoal morphology in semen specimens from 114 potentially fertile men, aged from 20 to 40 years, was evaluated from Papanicolaou stained smears, in order to investigate: (a) the frequency of abnormalities in the neck and tail of spermatozoa with an abnormal or normal head, and (b) the ability of prediction of the morphology of one sperm part when the morphology of another is known. It was found that: (1) Morphological abnormalities in the neck are significantly higher (p less than 0.001) in spermatozoa with an abnormal head than in spermatozoa with a normal head. (2) Morphological abnormalities in the tail and cytoplasmic droplet are also higher, although not significant, in spermatozoa with an abnormal head. (3) The proportional reduction in error (PRE) was low in all cases. Our results show that spermatozoa with abnormal heads more often present morphological abnormalities of their other parts than spermatozoa with normal heads. However, no prediction can be made on the nature of the morphology of a part of a spermatozoon on the basis of knowledge of the morphology of another of its parts.