Danazol is a derivative of the synthetic steroid ethisterone, a modified testosterone. It was approved by the U.S. Food and Drug Administration (FDA) as the first drug to specifically treat endometriosis, but its role as a treatment for endometriosis has been largely replaced by the gonadotropin-releasing hormone (GnRH) agonists.

The agent is fat-soluble and has a molecular weight of 337.5. Its CAS registry number is 17230-88-5.

Danazol decreases the pituitary hormones follicle-stimulating hormone and luteinizing hormone ( FSH and LH) and exerts an antiproliferative effect upon the endometrium, leading to amenorrhea. This effect is useful for patients with endometriosis. Commonly, pelvic pain associated with endometriosis is improved as well.

Androgenic side effects are of concern, because in sensitive female patients, danazol can enhance unwanted hair growth, leading to hirsutism. On rare occasion, it can deepen the voice. Other possible side effects include acne and oily skin. Because danazol is metabolized by the liver, it cannot be used by patients with liver disease, and in patients receiving long-term therapy, liver function must be monitored on a periodic basis. Some patients who use danazol experience weight gain and fluid retention. Due to these limitations, danazol is seldom prescribed continuously beyond six months.

Unlike GnRH agonists, danazol does not induce osteoporosis. Also, symptoms of hot flushes tend to be less common or severe.

Danazol is contraindicated in pregnancy because it could masculinize a female fetus.

Danazol has been used for other indications, namely in the management of menorrhagia, of fibrocystic breast disease, and of hereditary angioedema. Though Danazol prevents pregnancy, it is not licenced for use as a contraceptive agent.

In the United States, Danazol was initially marketed as Danocrine, before it became available as a generic drug.