Twenty-two patients with primary biliary cirrhosis were treated with ursodeoxycholic acid, 10 mg/kg per day. Fourteen patients with stages I/II were treated for 4-12 years (mean 7.5), and eight patients with stages III/IV for 5-12 years (mean 6.5). Twelve of 13 patients with early stages became asymptomatic. Aminotransferases, cholestasis-indicating enzymes and IgM improved (p < 0.01) and remained low during the whole treatment period. Ursodeoxycholic acid was the predominant serum bile acid, and lithocholic acid did not increase in the serum but did increase in the stool. Of eight patients with stages III/IV, seven were symptomatic, and four became asymptomatic. In all eight patients, laboratory data improved. Of these eight patients three experienced haemorrhage from oesophageal varices, two had to be transplanted, and one of them died. In one patient splenic rupture occurred, and in three liver function tests deteriorated. Although the number of patients was small, this is the longest treatment period so far reported. Ursodeoxycholic acid had no side effects for up to 12 years, and in patients with early stages it seemed to have a beneficial effect on symptoms and the progression of the disease. However, even with up to 12 years of therapy, ursodeoxycholic acid did not cause antimitochondrial antibodies to disappear either in the early or in the late stages, it was unable to prevent rebound effects during therapy intermission even after more than 5 years of continuous therapy, there was no decisive influence on liver histology and it did not cure the disease. Finally, although ursodeoxycholic acid improved life quality and laboratory data in all patients with late stages of the disease, it did not prevent complications due to cirrhosis.