In 15 patients with hepatocellular carcinoma (HCC) and 14 patients with liver cirrhosis (LC), urinary excretions of delta-aminolevulinic acid (ALA), porphobilinogen (PBG), uroporphyrin (UP), coproporphyrin (CP), and erythrocyte contents of CP and protoporphyrin (PP) were examined. In patients with HCC, urinary excretions of ALA and PBG and erythrocyte contents of CP and PP were not increased, but urinary excretions of UP and CP were significantly increased more than those of LC patients. Urinary excretions of UP and CP had no correlations with liver function tests and excretion of UP correlated slightly with blood hemoglobin level. After administration of ALA intravenously, urinary excretions of UP and CP were clearly increased in patients with HCC compared to normal controls. A Red fluorescent area was present at the cancerous area but not in the noncancerous cirrhotic area in a patient with HCC. These results suggest that aberrant porphyrin metabolism occurred in patients with HCC compared to other liver diseases.