Destruction of spermatogonial stem cells (SSCs) along the chemotherapy and radiotherapy is one of the side effects of cancer treatments that lead to infertility. In vitro propagation of hSSCs is necessary to obtain an adequate number of cells for successful transplantation. In this study, hSSCs were isolated from testis biopsies of the patients with maturation arrest and proliferated in DMEM in the presence of LIF and bFGF for 5 weeks. The various types of human spermatogonia were identified in culture system and compared with testis tissue using morphological criteria at the ultrastructural level. The results showed that although many various types of spermatogonia were identified, but no remarkable difference was observed between spermatogonial cells in culture system and testis tissue. Electron and light microscopic studies of hSSC colonies did not show differentiated SSCs in the culture system. The results also showed that probably the suitable time for transplanting of SSCs in recipient testis is 2-3 weeks after culture. Because apoptosis which may affect the development of germ cells has not started in colony cells at this time and the population of apoptotic cells are low.