he National Cooperative Gallstone Study (NCGS) was double- blind, randomized, controlled, multicenter clinical trial of 1,044 subjects to study the efficacy and safety of using the bile salt chenodiol (chenodeoxycholic acid) to dissolve gallstones. The study was funded through a contract from the National Institute of Diabetes, Digestive and Kidney Diseases. An initial study of 128 patients randomized to high or low dose chenodiol included liver biopsy periodically to assess potential hepatotoxicity. Subsequently, in a full-scale study, 916 patients were followed for 2 years of treatment, approximately one-third assigned to high dose chenodiol, low-dose chenodiol or placebo. The principal results (Schoenfield, Lachin et al., Annals of Internal Medicine, 1981) showed that chenodiol was marginally effective, achieving complete dissolution of gallstones in 13% of patients treated with the high dose, versus only 1% among those treated with placebo. Chenodiol, however, was potentially hepatotoxic and also lead to slight elevations in serum lipids. Based largely on the results of the NCGS, chenodiol was approved by the Food and Drug Administration as the first non-surgical treatment for gallstones. All total, 20 papers have been published by the LNCS group. NIDDK Contract N01- AM-0-2205, 1973-1984.