Background & Aims: Treatment of intrahepatic cholestasis of pregnancy with ursodeoxycholic acid appears promising, but data are limited so far. The aim of this randomized study was to evaluate the efficacy and safety of ursodeoxycholic acid in comparison with cholestyramine. Methods: Eighty-four symptomatic patients with intrahepatic choles-tasis of pregnancywere randomized to receive either ursodeoxycholic acid, 8- 10 mg/kg body weight daily (n = 42), or cholestyramine, 8 g daily (n = 42), for 14 days. The primary end point was a reduction of pruritus by more than 50% after 14 days of treatment as evaluated by a pruritus score. Secondary end points were outcome of pregnancy, reduction of serum aminotransferase activities and serum bile acid levels, and drug safety. Intention-to-treat analysis was applied. Results: Pruritus was more effectively reduced by ursodeoxycholic acid than cholestyramine (66.6% vs 19.0% , respectively; P < .005). Babies were delivered significantly closer to term by patients treated with ursodeoxycholic acid than those treated with cholestyramine (38.7 ± 1.7 vs 37.4 ± 1.5 weeks, respectively, P < .05). Serum alanine and aspartate aminotransferase activities were markedly reduced by 78.5% and 73.8% , respectively, after ursodeoxycholic acid, but by only 21.4% , each, after cholestyramine therapy (P < .01 vs ursodeoxycholic acid). Endogenous serum bile acid levels decreased by 59.5% and 19.0% , respectively (P < .02). Ursodeoxycholic acid, but not cholestyramine was free of adverse effects. Conclusions: Ursodeoxycholic acid is safe and more effective than cholestyramine in intrahepatic cholestasis of pregnancy. Background & Aims: Treatment of intrahepatic cholestasis of pregnancy with ursodeoxycholic acid appears promising, but data are limited so far. The aim of this randomized study was to evaluate the efficacy and safety of ursodeoxycholic acid in comparison with cholestyramine. Methods: Eighty-four symptomatic patients with intrahepatic choles-tasis of pregnancywere randomized to receive either ursodeoxycholic acid, 8-10 mg / kg body weight daily (n = 42), or cholestyramine, 8 g daily (n = 42) was a reduction of pruritus by more than 50% after 14 days of treatment as evaluated by a pruritus score. Secondary end points were outcome of pregnancy, reduction of serum aminotransferase activities and serum bile acid levels, and drug safety. Intention-to-treat analysis was applied. Results: Pruritus was more particularly reduced by ursodeoxycholic acid than cholestyramine (66.6% vs 19.0%, respectively; P <.005). Babies were delivered significantly closer to te rm by patients treated with ursodeoxycholic acid than those treated with cholestyramine (38.7 ± 1.7 vs. 37.4 ± 1.5 weeks, respectively, P <.05). Serum alanine and aspartate aminotransferase activities were markedly reduced by 78.5% and 73.8%, respectively, after ursodeoxycholic Endogenous serum bile acid levels decreased by 59.5% and 19.0%, respectively (P <.02). Ursodeoxycholic acid, but not cholestyramine (P <.01 vs ursodeoxycholic acid) was free of adverse effects. Conclusions: Ursodeoxycholic acid is safe and more effective than cholestyramine in intrahepatic cholestasis of pregnancy.