Sperm cryopreservation has revolutionized the field of assisted reproduction. However, it causes cryodamage to the structure and function of spermatozoa during the freezing-thawing process. Optimization of sperm cryopreservation is necessary for the preservation of male fertility. Cryodamage can be reduced effectively by such methods as improvement of semen quality before freezing, spermatozoal selection, addition of optimal cryoprotectants and application of appropriate thawing techniques. Recent studies focus on cryobiology, improvement of freezing-thawing methods, especially for poor quality semen, and evaluation criteria for post-thaw spermatozoa.