Advances in the treatment of male infertility-specifically intracytoplasmic sperm injection have now resulted in greater recognition of the clinical significance of genetic translocations. This article focuses on the different types of translocations (Robertsonian, reciprocal) as well as on the prevalence and incidence of translocations in infertile and other populations. The authors contrast theoretical and empiric meiotic segregation patterns in the different clinical settings of traditional prenatal genetic diagnosis and preimplantation genetic diagnosis. In particular, the significance of a higher prevalence of unbalanced blastomeres is discussed.