A 5-year-old boy and his 2 1/2-year-old sister developed cyanosis and digital clubbing after the onset of hepatitis of undetermined etiology. Multiple, small, pulmonary arteriovenous fistulas seemed to be primarily responsible for the systemic arterial oxygen desaturation. Overt cyanosis appeared when pathological changes of liver disease were minimal. After the liver disease gradually subsided in the boy, his cyanosis, clubbing, and arterial desaturation completely disappeared. The liver disease was progressive in the girl, and her acquired cardiovascular abnormalities were fatal. Pulmonary arteriovenous fistulas were delineated by postmortem injections of viscous radiopaque material. The observations suggest that liver injury may be the important event in initiation and maintenance of arteriovenous shunting in susceptible individuals.