Changes in urinary prostaglandin E2 (PGE2), 6-keto PGF1 alpha, and thromboxane (TXB2) excretion in 12 patients with obstructive jaundice were observed in relation to renal function and the renin-angiotensin (R-A) system. In obstructive jaundice before percutaneous biliary drainage the creatinine clearance (CCr) was significantly lower (p less than 0.001) and the PGE2 and plasma angiotensin II (AII) concentrations were significantly higher (p less than 0.005 and p less than 0.005, respectively) than those in normal subjects. Both 6-keto PGF1 alpha and TXB2 were widely distributed. When CCr returned to normal after drainage, PGE2 and plasma AII also returned to normal, but when CCr decreased after drainage, PGE2 and plasma AII increased. Before drainage, PGE2 correlated negatively with CCr (r = -0.72, p less than 0.01) and positively with plasma AII(r = 0.69, p less than 0.02). 6-Keto PGF1 alpha correlated positively with serum total bilirubin (r = 0.66, p less than 0.02). The percentage change in PGE2 after drainage correlated negatively with that in CCr (r = -0.95, p less than 0.005). The percentage chang in plasma AII correlated positively with that in urine PGE2 (r = 0.94, p less than 0.005) and negatively with that in CCr (r = -0.85, p less than 0.02). These results suggest that PGE2 is closely related to the R-A system and might assist in the maintenance of renal circulation in obstructive jaundice.