Eighteen semen samples were collected from 18 normospermic men. Two aliquots (1 mL) were prepared from each ejaculate, washed with Ham's F-10, and each washed sperm pellet was reconstituted in 2 mL volume of Ham's F-10 medium. Each aliquot one was stained using the AO-staining method. Each aliquot two was filtered via the SpermPrep II method, and the recovered spermatozoa were stained similarly. The proportion of single-stranded DNA (red) spermatozoa to double-stranded (green) spermatozoa was significantly higher in aliquot one than in the postfiltered sample (aliquot two), suggesting that the SpermPrep filtration procedure selectively entrapped the spermatozoa with abnormal DNA.