The measurement of ovarian volume has been recently shown to predict follicular response in in-vitro fertilization (IVF), specifically a lower number of retrieved oocytes with decreasing ovarian volume. This test appears to be better than basal follicle-stimulating hormone (FSH) as a prognostic measure of ovarian reserve, However, the effect of pituitary desensitization on ovarian volume has not been previously investigated. We prospectively evaluated 38 women undergoing IVF using a long luteal leuprolide acetate (LA) protocol. All women had their ovarian volume measurements performed on day 21, the day of LA start, and again an the day of gonadotrophin start. The mean age was 30.6 +/- 3.9 years (range 23-37). Basal FSH was 5.4 +/- 1.9 IU/l (range 1.2-10.2), The mean preLA ovarian volume was 7.0 +/- 3.6 cm(3) (left ovary 6.8 +/- 3.9, right ovary 7.1 +/- 3.8), compared to 6.3 +/- 4.2 cm(3) postLA (left ovary 6.0 +/- 4.9, right ovary 6.5 +/- 4.8) (not significant). The mean number of small antral follicles noted in both ovaries was also unchanged after pituitary desensitization. Pituitary desensitization using LA had no effect on overall ovarian volume measurements. The total number of retrieved oocytes decreased with increasing age and decreasing ovarian volume.