Many chemotherapy and radiation-containing regimens for cancer or prior to bone marrow transplantation can cause sterility in children and young adults. In addition, some human disease conditions (e.g., Klinefelter's) are associated with infertility. Semen cryopreservation is available as a fertility-preserving option for post pubertal boys and adult men, but many do not take advantage of this option due in part to lack of information, illness, and/or time constraints relative to their treatment plan. Currently, no fertility-preserving options are available for prepubescent boys who are not yet producing sperm. The primary objective of the proposed study is to 1) Optimize techniques for cryopreserving testicular tissue, 2) Assess malignant contamination in testicular tissues and 3) develop methods to enrich spermatogonial stem cells and remove malignant contamination from testicular tissue. In addition, this study will process and cryopreserve tissue and/or cells for participating patients as a resource for future elective procedures to attempt fertility restoration.