The domestic dog(Canis familiaris) is one of the most valuable model animals for biomedical research. However,the canine reproductive physiology differs from that of other mammalian species studied to date. The efficiency of in vitro oocyte maturation is very low in this species,which limits the use of canine in the biological research. In vivo,the canine oocytes are exposed to a high concentration of progesterone in the follicular environment before ovulation,and they are released at the germinal vesicle stage. Oocytes then resume and complete meiosis within the oviduct. The conditions for in vitro maturation of dog oocyte may differ from those of other mammalian species. Currently,M199 medium containing several maturation factors is generally used for in vitro maturation culture of canine oocytes,but only 15%-20% of ovarian oocytes reach the metaphase Ⅱ stage. Therefore,an efficient in vitro culture system should be based on in vivo conditions in order to create a microenvironment similar to that in which oocyte development occurs physiologically. But,little is known about mechanisms regulating oocyte maturation in the dog. This review analyzes the known factors involved in canine oocyte maturation in vivo and in vitro in order to provide useful data for future development of modified canine oocyte maturation system.