Objective: To determine whether a new ovarian stimulation protocol termed 'minimal stimulation' provides pregnancy rates (PRs) comparable with those in a conventional full stimulation protocol for patients undergoing assisted reproductive technologies (ART). Design: Prospective, nonrandomized study of patients in minimal stimulation or full stimulation, followed by standard IVF and zygote intrafallopian transfer or uterine-ET. Setting: The ART program of the Mayo Clinic, Rochester, Minnesota. Patients: Women (n = 120) 42 years of age or younger with serum day 3 FSH level ≤ 15.0 mIU/mL (conversion factor to SI unit, 1.0), normal thyroid-stimulating hormone and PRL levels, normal endometrial cavity as observed on hysterosalpingogram, and partners with a normal semen analysis. Interventions: Oral clomiphene citrate, hMG, oocyte retrieval, IVF-ET. Main Outcome Measures: Cancellations, implantation, pregnancy. Results: The cancellation rate was not significantly higher in minimal stimulation (25.8%) than in full stimulation (14.1%). Minimal stimulation cycles yielded fewer oocytes per aspiration (3.4 ± 1.6) than full stimulation (10.1 ± 5.4). There was no difference in the implantation rates per ET (minimal stimulation, 16.4%; full stimulation, 13.3%) or overall clinical PRs per retrieval (minimal stimulation, 31%; full stimulation, 42%). Conclusions: Minimal stimulation for IVF is less expensive than full stimulation and minimizes monitoring and patient discomfort. In addition, it produces acceptable PRs and represents an attractive alternative to select patients undergoing ART.