The effectiveness of clomiphene citrate is demonstrated in the treatment of subfertility associated with oligo-ovulation. Clomiphene citrate acts as a central estrogen receptor blocker, which results in increased production and secretion of follicle stimulating hormone (FSH). The physiologic effects and clinical benefits in ovulatory women with unexplained subfertility are less clear. The drug is associated with the side effect of increased risk of multiple pregnancy and a suggestion of potentially increased ovarian cancer risks. In light of these concerns, defining the effectiveness of clomiphene citrate for ovulatory women with unexplained subfertility is extremely important.