Spontaneous mutations in inbred strains provide valuable resources for new disease models. Unfortunately, these mutations may affect reproduction, which require considerable efforts in breeding management. We transplanted ovaries of such mutant rat strains orthotopically into ovariectomized premature coisogenic recipients. A reproductive cycle was established in each of the recipients within 5 to 6 weeks after transplantation. Moreover, one-third became pregnant and had litters an average of 3 months after transplantation. These experiments demonstrate that orthotopic transplantation of ovaries can be used in the management of subfertile rat colonies.