The aim of our work was to define and better understand apoptosis in the spermatozoa of normal subjects, infertile patients and patients affected by specific tumoral diseases employing the method of the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling and confirming the results by electron microscopy. We studied 23 healthy, normozoospermic subjects (group A), 29 oligoasthenoteratozoospermic patients, affected by various andrological pathologies (group B), 28 patients with Hodgkin's disease (C1) and 30 patients with testicular cancer (C2). Our data demonstrate that the percentage of apoptosis in normozoospermic subjects (group A) is significantly lower than in all the other groups (B, C1, C2) (P < 0.001). This confirms that high DNA fragmentation is one of the characteristics of spermatogenetic failure. The induction of apoptosis, which can also be a basic response to neoplastic disease, can even act right up to the mature male gamete. Our results suggest that apoptosis could be the final result of various pathologies and of a deregulation of spermatogenesis control systems.