Incidence of liver disease (LD) associated with cystic fibrosis (CF) and its clinical characterization still is unsettled. We have assessed prospectively the incidence and risk factors of this complication, and its impact on the clinical course of CF. Between 1980 and 1990, we enrolled 177 CF patients without LD in a systematic clinical, laboratory, ultrasonography screening program of at least a 10-year duration. During a 14-year median follow-up (2,432 patient-years), 48 patients developed LD, with cirrhosis already present in 5. Incidence rate (number of cases per 100 patient-years) was 1.8% (95% confidence interval: 1.3-2.4), with sharp decline after the age of 10 years and higher risk in patients with a history of meconium ileus (incidence rate ratio, 5.5; 2.7-11), male sex (2.5; 1.3-4.9), or severe mutations (2.4; 1.2-4.8) at multivariate analysis. Incidence of cirrhosis was 4.5% (2.3-7.8) during a median period of 5 years from diagnosis of liver disease. Among the 17 cirrhotic patients, 13 developed portal hypertension, 4 developed esophageal varices, 1 developed liver decompensation requiring liver transplantation. Development of LD did not condition different mortality (death rate ratio, 0.4; 0.1-1.5) or higher incidence of other clinically relevant outcomes. In conclusion, LD is a relatively frequent and early complication of CF, whose detection should be focused at the first life decade in patients with history of meconium ileus, male sex, or severe genotype. Although LD does not condition a different clinical course of CF, in some patients it may progress rapidly and require liver transplantation.