A male patient with Wilson's disease developed a hepatocellular carcinoma after treatment for nine years with D-penicillamine. Examination at necropsy showed that excess liver copper had been effectively removed. As copper has been shown to protect against chemically induced hepatocellular carcinoma in rats, this may be the reason for the extreme rarity of hepatocellular carcinoma in patients with Wilson's disease and possibly in other liver diseases with hepatic copper overload.