Headless or unucleated spermatozoa were evaluated in semen specimens of 52 fertile men in order to investigate the frequency and the percentage of this morphological abnormality and to estimate the probable correlation of the abnormality with other semen parameters, since there are no available data. The only sperm parameter which correlated with the number of headless spermatozoa was the number of micro round-headed spermatozoa (r= + 0.4432, P<0.001). It is concluded that the high frequency of headless or unucleated spermatozoa in the semen specimens of fertile men, albeit in low percentage, does not seem to have any biological significance. Moreover headless and round-headed spermatozoa could be the outcome of the same pathogenetic mechanism.