The incidence of aneuploidy was estimated for chromosomes 8, 9, 13, 16, and 21 in mature human spermatozoa by primed in situ (PRINS) labeling technique. This method allows us to perform a chromosome-specific detection by in situ annealing of a centromeric specific primer. A dual color PRINS protocol was adapted to human sperm. The decondensation and the denaturation of sperm nuclei were simultaneously performed by 3-M NaOH treatment. Double labeling of spermatozoa was obtained in <2 h. A total of 96,292 sperm nuclei were analyzed by two independent observers. The estimates of disomy were 0.31% for chromosome 8, 0.28% for chromosome 9, 0.28% for chromosome 13, 0.26% for chromosome 16, and 0.32% for chromosome 21. These homogeneous findings suggest an equal distribution of aneuploidies among autosomal chromosomes in males.