137. Pollard et al. 138 investigated the pregnancy defect in the osteopetrotic op/op mouse, demonstrating a requirement for CSF-1 in female fertility. Uterine epithelium, a source of CSF-1, is associated with recruitment of SR-A+ macrophages, thought to contribute to growth and remodeling during the menstrual cycle (J. Brandon, unpublished observations). Endometriosis is a poorly understood condition where ectopic epithelial cells induce peritoneal inflammation, associated with a distinct pro-inflammatory macrophage population, revealed by network analysis 139. The gene discussed is CSF1; the disease is endometriosis.