Clomiphene citrate (Clomid) and letrozole (Femara) are two different oral medications used to treat women who have problems with ovulation and infertility. The two medications work in different ways to help the pituitary gland release more follicle-stimulating hormone (FSH) and therefore improve the stimulation of developing follicles (egg sacs) in the ovaries. Women with ovulation disorders -especially those with polycystic ovarian syndrome (PCOS) - often have absent or irregular menses, and they do not ovulate or ovulate infrequently. PCOS is a condition in which there can be many variable and subtle symptoms, and it is estimated that between 1 in 10 and 1 in 20 women of childbearing age have this hormonal disorder. For more than 50 years, clomiphene citrate has been the preferred drug to help patients, including those with PCOS, ovulate. However, while ovulation rates are generally good, the pregnancy rates remain relatively low, so there may be certain indications in which letrozole may be the drug of choice.