Men with testicular neoplasia (TN) and Hodgkin's disease (HD) are those who more frequently require treatment for fertility because these malignancies affect patients during the reproductive age and because the early diagnosis and the improved anti-neoplastic treatments cure most of these patients. Although some of them can father a child spontaneously, assisted reproductive techniques allow fatherhood to patients with severe spermatogenesis impairment and this possibility has raised concern about the long-term consequence of the testicular damage induced by chemo- and/or radiotherapy. This paper reviews the effects of cancer per se and of anti-neoplastic treatments on gonadal function, sperm aneuploidy rate and sperm DNA integrity. A debate is still open as to whether TN or HD per se may impair spermatogenesis. Many studies have shown that this is the case, albeit others have challenged this view. Chemo- and/or radiotherapy affects negatively gonadal function, rendering almost all patients azoospermics. However, spontaneous pregnancies and a high degree of spermatogenesis recovery occur with time. A large body of literature on sperm chromosome complement suggests an increased rate of structural and numerical chromosome abnormalities in patients with cancer during anti-neoplastic treatment. A minority of them has, however, shown that this effect disappears with time. An interesting and relatively new aspect is the study of sperm DNA integrity in patients with TN and HD particularly following chemo- and/or radiotherapy. The scanty information available seems to suggest that these patients have a permanent or at least a long-lasting DNA fragmentation in their spermatozoa.