We report the use of the PRimedIN Situ (PRINS) labelling technique for the direct estimation of disomy rates for various chromosomes in human sperm. The PRINS technique provides a rapid and reliable method for chromosome screening since specific labelling may be obtained in less than 2 h. In the present study, the disomy rates of chromosomes 2, 5, 9, 12 and 18 were investigated. The incidences of disomy are similar for all these chromosomes, ranging from 0.27% to 0.33%. These findings suggest an equal distribution of aneuploidies among autosomes in human sperm.