Summary—Flow cytometric studies of spermatogenesis have been advanced by the need for: i) rapid, sensitive, objective and multiparameter measurements of reproductive effects due to environmental, occupational, and therapeutic exposure to toxicants; and ii) assessment of fertility potential of human and animal sperm. As a consequence, various flow cytometric techniques are already available to identify germ cell subpopulations undergoing both proliferative and maturative processes in normal and perturbed conditions. Significant improvements have been introduced in order to investigate the spermatogenic complex differentiation pathway and the apparent uniformity of mature sperm. Flow cytometry (FCM) has been applied to the measurement of both testis and sperm cells in a variety of species, including man. End points considered in toxicology studies are: altered testicular germ cell ratios, DNA and RNA content, increase of the coefficient of variation, induction of diploid elongated spermatids and diploid sperm, altered nuclear morphology, sperm cell viability, mitochondrial function and sperm chromatin structure. Precise DNA content measurements allow accurate analysis to determine the proportion of X‐ and Y‐chromosome bearing sperm and sorting of these subpopulations for gender preselection. FCM technology has reached a maturation level that allows its inclusion in the list of available and routine methods for reproductive studies in human and animal popula