This paper reports the successful pregnancy in rats with only 10-20% of ovarian tissue. Sprague-Dawley female rats of breeding age were divided into five groups: group 1 (completely ovariectomized), the ovaries from both the sides of the rats were removed completely; group 2 (partially ovariectomized, 80-90% of the ovary of each side was removed leaving the remaining tissue in place; group 3 (ovariectomized with flank transplant), the ovary of each side was removed from the ovarian stalk and inserted into a subcutaneous pocket made surgically in the flank on the respective side of the same rat; group 4 (partially ovariectomized with flank transplants), 80-90% of the ovarian mass was removed from the ovarian stalk and put back in the flank position in the subcutaneous pocket on the same side; group 5 (control), rats with intact ovaries. Estrous cyclicity, mating behavior and pregnancy rate were recorded in the animals. Percent rats cycled were 0.00, 80.00, 80.00, 70.00 and 100 in groups 1-5 respectively; percent cycled rats mated were 86.27, 100, 71.42 and 100 in groups 2-5 respectively; and percent mated rats reaching successful pregnancy were 36.36, 0.00, 100 and 100 in groups 2-5 respectively. Pregnancy rate in the mated rats in group 2 was lower than that of groups 4 (P < 0.01) and 5 (P < 0.01), whereas, it did not differ among groups 4 and 5.(ABSTRACT TRUNCATED AT 250 WORDS)