While cancer, and especially testicular cancer and Hodgkin's disease, affects male fertility in many ways, the current increase of survival of male cancer patients of reproductive age or earlier has emerged as a new challenge to their subsequent ability to father children. Cancer treatments, including surgery, radiotherapy and chemotherapy, can have a transitory as well as a permanent detrimental impact on male fertility. Gonadotoxic effects and the length of time for sperm recovery after radiotherapy depends not only on initial semen quality, but also on gonadal dosage and the delivery method after chemotherapy, on the type of regimens and dosages and on the spermatogenesis phase that each drug impacts. Combination treatment with radiotherapy and chemotherapy will induce more gonadotoxicity than either modality alone. Although efforts to prevent gonadal toxicity in cancer treatment are routinely applied, sperm cryopreservation remains the gold standard to maintain male fertility after cancer survival. Fertility preservation for prepubertal boys presents the greatest problem due to the absence of mature sperm in their gonads. In this area, research efforts are concentrated on cryopreservation of immature gametes and, in particular, techniques for their maturation and proliferation after thawing.