To clarify the efficiency of superovulation in immature female rabbits, immature female rabbits were superovulated with equine chorionic gonadotropin, and the number of recovered oocytes, their maturity, and their ability to develop into blastocysts under in vitro fertilization and culture were examined in this study. More than 80 oocytes were recovered from 12-14-week-old immature female rabbits. In particular, an average of more than 100 oocytes were recovered from 13-week-old immature female rabbits. The number of oocytes in immature female rabbits was significantly-approximately 4 times-higher than in mature female rabbits. To compare oocyte maturity, oocytes from immature and mature female rabbits were compared by brilliant cresyl blue staining and mitochondrial distribution analysis. The proportion of mature oocytes detected by brilliant cresyl blue staining was higher in oocytes from mature female rabbits than in oocytes from immature female rabbits, but there were no significant differences in active mitochondrial distribution, fertilization rate, or blastocyst development rate. These results indicate that superovulation with immature female rabbits may be a useful technique for the collection of many oocytes.