The proliferative activity and angiogenic factors of pelvic endometriosis and uterine endometrium and their correlation with different pigmented lesions are important throughout the menstrual cycle. The proliferative activity and/or expression of angiogenic factors appears to be different between endometrium and endometriosis, and also different in each pigmented lesion. Immunohistochemical studies using computerized image analysis have shown that in normal endometrium, the PCNA index shows cyclic variation, but no cyclic change is observed in endometriosis. In the pelvic peritoneum, the PCNA index is higher in red lesions compared to black and white lesions. There is no difference in VEGF expression among different pigmented lesions. However, a cyclic variation of VEGF concentration was found in the peritoneal fluid of patients with endometriosis. As a newly determined angiogenic factor, the number of endoglin-positive cells and the mean endothelial area were higher in red lesions than in black or white lesions. These results suggest that the pathogenesis and activity of endometriosis possibly depends on internal angiogenesis. The cellular activity of endometriotic lesions may not necessarily coincide with the regulation of angiogenesis, and may not be synchronized in each pigmented pelvic lesion of endometriosis.