To determine the practicality of controlled ovulation of the dominant follicle as a technique to study meiotic maturation of oocytes during contraceptive research, we developed a technique for aspiration of the single dominant follicle using a dual-needle continuous irrigation technique 27 hours after an ovulatory stimulus. All of the oocytes (3/3) recovered from control animals, but only 1/6 (17%) of oocytes from animals treated with the meiotic inhibitor ORG 9935 exhibited germinal vesicle breakdown, indicating resumption of meiosis.