In order to investigate the effectiveness of microporous cholestyramine in the pharmacological management of intra- and extrahepatic cholestasis, a double-blind placebo-controlled study was carried out in 10 patients. Microporous cholestyramine or placebo 3 g t.i.d. were given orally over a four-week period. The active drug resulted statistically superior to the placebo in reducing itching intensity (p less than 0.01) and serum bile acids (p less than 0.01). A positive linear relationship between itching and serum bile acids (p less than 0.01) was also demonstrated.