A study of reticulo-endothelial function was performed in 30 patients with obstructive jaundice. Reticulo-endothelial phagocytic function, measured by the clearance of intravenous human micro-aggregated albumin, was significantly depressed in jaundiced patients compared with non-jaundiced controls (P less than 0.001). There was a significant correlation (P less than 0.001) between phagocytic function and plasma bilirubin level but not with transaminase or bile salt level. Phagocytic function was not related to the presence of malignancy, but was markedly reduced in patients with cholangitis. There was no reduction in hepatic sinusoidal blood flow, opsonin levels (fibronectin, IgG, complement) or serum opsonic activity to account for the reticulo-endothelial dysfunction.