Ursodeoxycholic acid (UDCA), 7beta hydroxy epimer of chenodeoxycholic acid (CDCA), has been used as a choleretica for 20 years in Japan. Recent report showing increased excretion of UDCA in bile after CDCA administration may suggest the possibility that UDCA has similar effects to CDCA on bile cholesterol unsaturation and on gallstone dissolution. The present paper describes the clinical usefulness of UDCA for gallstone patients during the past two years. Seventy-four gallstone patients with functioning gall-bladders, 19 men and 55 women with a mean age of 48 years, have been treated for 6 months or more. UDCA, supplied in tablets (Ursosan), was given 450 mg per day. The disappearance or the reduction of stone size or number, or both (dissolution effect) was recognized in 32 out of 74 patients (43%). In case of radiolucent stones, the overall effective rate was estimated for 24 of 46 patients (52%). There may be no significant difference in dissolution effect between CDCA and UDCA treatment, however, the merit of UDCA treatment seems to have its few side effects.