Ovaries from homozygous diabetic (db/db) female mice were removed and transplanted into the empty left ovarian sacs of normal homozygous (m/m) female mice which had undergone left oophorectomies. To produce controls, the previously removed normal left ovaries were transplanted into the empty left ovarian sacs of other normal (m/m) left oophorectomized females. Glucose tolerance tests were done on the study and control mice before surgery, after surgery, during pregnancy, and after delivery. There were no significant differences in the glucose tolerance test results between study group and controls before or after surgery. However, the study group, when compared to the controls, had a statistically significant glucose intolerance during pregnancy. After delivery, the glucose levels returned to normal. The ovaries from diabetic (db/db) female mice may produce hormones which, by themselves or in concert with the fetal and placental hormones, may produce maternal glucose intolerance during pregnancy.