In this study, the effectiveness of ursodeoxycholic acid (UDCA) therapy on the dissolution of gallstones, side effects, changes on the natural history of gallstones disease, complications, recurrence rates and factors which affects the succes rate were investigated. Sixty two minimally symptmatic patients with gallstones were included in the study. All stones which were smaller than 5 mm and 58% of stones smaller than 10 mm were successfully dissolved. The succes rate in stones larger than 10 mm or multiple stones was low (8.7%). There was no serious side effect except mild diarrhea. Disadvantages of this therapy are its long duration, high cost and high recurrence rate. Careful patient selection increases the success rate in this therapy. It has few side affects is safe, and may therefore be an alternative to surgical treatment in suitable cases.