Forty-one patients with gestational diabetes requiring insulin were enrolled in a randomized study to investigate the efficacy of an exercise program in normalizing glucose tolerance. Seventeen of 21 patients completed the exercise program while maintaining normoglycemia and obviating insulin therapy. Maternal and neonatal complications did not differ between the study and control groups. The type of program described appears to be safe and can serve as a model for exercise prescription for pregnant diabetic women to attain improved glucose tolerance.