Patients with oligoasthenoteratozoospermia (OAT) and normal karyotypes have an increased sperm aneuploidy rate. This may be due to an altered intratesticular environment that affects the chromosomal segregation mechanism(s). Alternatively, it may be due to a generalized meiotic and mitotic abnormality. In this case, patients with abnormal spermatogenesis should also have an increased somatic cell aneuploidy rate. To test this hypothesis, we evaluated peripheral leukocyte aneuploidy rate in patients with spermatogenic impairment.In all, 38 patients were enrolled, of whom 20 had OAT, 15 non-obstructive azoospermia and three Y chromosome (Yq) microdeletions (AZF). Eight healthy normozoospermic men with proven fertility were recruited as controls. Conventional karyotype analysis, AZF microdeletion evaluation and triple-colour FISH for chromosomes X, Y and 12 were conducted in all patients and controls. A total of 1000 lymphocytes were scored for each patient and control.All patients and controls had a normal karyotype. Sex chromosome aneuploidy rates in peripheral lymphocytes was significantly higher in patients with OAT (0.74+/-0.09%), azoospermia (1.15+/-0.15%) or Yq microdeleted (1.54+/-0.40%), compared with controls (0.15+/-0.03%) (P <0.05).Patients with OAT, azoospermia or Yq microdeletions had a slight, but significant, increase of sex chromosome aneuploidy rate in lymphocytes, suggesting the presence of a generalized defective cell division mechanism. In contrast with recent observations, Yq microdeletions do not seem to predispose to a higher number of malsegregation events in somatic cells compared with patients with azoospermia.