With advances in cancer treatment, such as cytotoxic chemotherapy and radiotherapy, grave new sequelae of treatment have emerged for young cancer survivors. One sequela that cannot be overlooked is male infertility, with reportedly 15% to 30% of cancer survivors losing their fertility potential. Cytotoxic therapy influences spermatogenesis at least temporarily, and in some cases, permanently. The degree of spermatogenesis impairment depends on the combination of drugs used, their cumulative dose, and the level of radiation. The American Society of Clinical Oncology has created an index to classify the risks to fertility based on treatment. Medical professionals currently use this risk classification in fertility preservation (FP) programs. FP programs are currently being promoted to prevent spermatogenesis failure resulting from cancer treatment. For patients who are able to ejaculate and whose semen contains sperm, the semen (sperm) is cryopreserved. Moreover, for patients who lack the ability to ejaculate, those with azoospermia or severe oligozoospermia, and those who have not attained puberty (i.e., spermatogenesis has not begun), testicular biopsy is performed to collect the sperm or germ cells and cryopreserve them. This method of culturing germ cells to differentiate the sperm has been successful in some animal models, but not in humans. FP has recently gained popularity; however, some oncologists and medical professionals involved in cancer treatment still lack adequate knowledge of these procedures. This hinders the dissemination of information to patients and the execution of FP. Information sharing and collaboration between reproductive medicine specialists and oncologists is extremely important for the development of FP. In Japan, the network of clinics and hospitals that support FP is expanding across prefectures.