Arimidex® (generic name is anastrozole) is a very new drug developed for the treatment of advanced breast cancer in women. It is manufactured by Zenica Pharmaceuticals and was approved for use in the United States at the end of December 1995. Specifically, Arimidex® is the first in a new class of third-generation selective oral aromatase inhibitors5°. It acts by blocking the enzyme aromatase, subsequently blocking the production of estrogen. Since many forms of breast cancer cells are stimulated by estrogen, it is hoped that by reducing amounts of estrogen in the body the progression of such a disease can be halted. This is the basic premise behind Nolvadex®, except this drug blocks the action and not production of estrogen.