Endometriosis is defined as the presence of endometrial tissue (stromal and glandular) outside the normal uterine cavity. Conventional medical and surgical treatments for endometriosis aim to remove or decrease the deposits of ectopic endometrium. The observation that hyper androgenic states (an excess of male hormone) induce atrophy of the endometrium has led to the use of androgens in the treatment of endometriosis. Danazol is one of these treatments. The efficacy of danazol is based on its ability to produce a high androgen and low oestrogen environment (a pseudo menopause) which results in atrophy of the endometriotic implants and thus an improvement in painful symptoms.