27 patients with radiolucent biliary stones in normofunctioning gall bladder were treated with a combination of CDCA and UDCA (CDCA doses = 7.7 mg/kg/day; UDCA--6.5 mg/kg/day); only 23 continued in the study for at least one year. The reasons for leaving were in one case the necessity of a cholecystectomy and treatment interruption in 3 cases. The rate of complete dissolution was of 39%, being of 17% the partial dissolution rate. The only biochemical alteration was the increase of HDL cholesterol at 9 and 12 months of treatment (p less than 0.05 and p less than 0.01 respectively). Transient diarrhea was seen in 17% of the patients and it did not require treatment. The incidence of liver colic during the year before treatment was 26% and it decreased during the 1st year of treatment to 4%. The non-specific dyspepsia observed during the year before treatment was of 48%, and decreased to 17% during the first year of treatment. Only one patient developed calcification of the gallstone, 12 months after treatment.