Three experiments were performed to examine the administration of low doses of follicle-stimulating hormone (FSH) to induce turnover of follicles that are damaged upon summer thermal stress and to examine whether this FSH administration has beneficial effects on preovulatory follicles. In experiment 1, synchronized heifers were treated with 100 mg of Folltropin-V (n 7) or 4.4 mg of Ovagen (n 6) on day 3 of the estrous cycle. Treatment with both FSH sources resulted in greater (P 0.05) numbers of follicles than in control animals (n 12) on day 6 of the estrous cycle, indicating that low doses of FSH can increase the number of emerging follicles in a follicular wave. In experiment 2, milking cows were assigned to a control group (n 4) or treated with 2.2 mg (FSH-2.2; n 6) or 4.4 mg (FSH-4.4; n 5) Ovagen