The association between hepatocellular carcinoma (HCC) and cirrhosis provides a formidable means for prospectively studying patients who are at risk of HCC. Early diagnosis of HCC is possible not only due to knowledge of the risk factors for this tumor, but also because HCC has a very long phase of intrahepatic growth and tends to grow as a solitary mass. Early diagnosis is also possible because sensitive and relatively inexpensive diagnostic tools are available. Several prospective studies of Oriental and Western patients with cirrhosis now in progress have led to the identification of many patients with small tumors. However, in the face of this evidence that screening high-risk patients may increase the yield of subclinical small tumors, no firm conclusion has yet been reached on whether early diagnosis of HCC may also increase the number of operable patients and reduce the mortality rate for this tumor.