Analyses of the dimensions and morphology of spermatozoa can be useful in the identification of mammalian species. We compared and contrasted sperm morphology and dimensions in 9 genera and 18 species of the family Cricetidae. Spermatozoa were obtained from the cauda epididymes of animals previously fixed in 10% formalin, and stained with Giemsa or silver-nitrate staining methods. At least 50 spermatozoa from different specimens were examined for each species. Discriminant function analysis was used to distinguish between the spermatozoa of different species and to identify the best discriminating characteristics. MANOVA revealed that differences between species were significant. Species in the same genus tended to group together. Qualitative characteristics that discriminate between species are discussed.