Excessive endometrial angiogenesis is proposed as an important mechanism in the pathogenesis of endometriosis. Evidence is reviewed for the hypothesis that the endometrium of women with endometriosis has an increased capacity to proliferate, implant and grow in the peritoneal cavity. Data is summarized indicating that the endometrium of patients with endometriosis shows enhanced endothelial cell proliferation. Results are also reviewed indicating that the cell adhesion molecule integrin alphavbeta3 is expressed in more blood vessels in the endometrium of women with endometriosis when compared with normal women. Taken together, these results provide evidence for increased endometrial angiogenesis in women with endometriosis when compared with normal subjects. Endometriosis is one of the family of angiogenic diseases. Other angiogenic diseases include solid tumours, rheumatoid arthritis, psoriasis and diabetic retanopathy. Excessive endometrial angiogenesis suggests novel new medical treatments for endometriosis aimed at the inhibition of angiogenesis.