The objective of this application is to identify a pharmacologic agent which helps couples in whom the female partner ovulates regularly successfully obtain their goal of delivering a healthy child, whose use will result in low rates of multiple gestations. The central hypothesis is that, in infertile ovulatory women undergoing ovarian stimulation (OS) and intrauterine insemination (IUI), the use of aromatase inhibitors (AI) will stimulate the ovaries sufficiently to produce no reduction in the rate of pregnancy, while significantly reducing the numbers of multiple gestational pregnancies that result from stimulation with clomiphene citrate (CC) or follicle stimulating hormone (FSH). The rationale for the proposed research is that reduction of multiple pregnancy rates could significantly reduce maternal and neonatal morbidity and mortality, as well as the cost of healthcare for these individuals and society.