We report the results of a multicenter study on the diagnosis and interventional therapy of hepatocellular carcinoma (HCC). The first aim--diagnosis--was to evaluate the sensitivity of 4 imaging techniques, namely ultrasonography (US), Computed Tomography (CT), digital arteriography (DSA) and Lipiodol CT (LCT), in HCC detection. The accuracy of these techniques was also investigated in tumor staging, which is important for treatment planning. Two hundred ninety patients underwent this imaging protocol. The patients were classified by tumor spread into three groups, namely group 1 (single HCCs 80 cc). US and CT diagnosed more cases as group 1 and fewer cases as group 3 than DSA and LCT; the latter two techniques gave a similar classification. With LCT as the gold standard, US and CT understaged 27.9% and 26.5% of cases, respectively. Even though LCT is known to have 53% sensitivity, it is currently the most sensitive preoperative investigation and therefore the best tool for treatment planning. In surgical patients, however, intraoperative US, with its nearly 100% sensitivity, is suggested. The second aim--treatment--consisted in assessing the therapeutic efficacy of intraarterial chemoembolization (CEAT) versus percutaneous ethanol injection (PEI) in non advanced HCC and of CEAT versus no treatment (NT) in advanced HCC. Treatment efficacy was evaluated with the following randomized protocols: PEI versus CEAT in group 1, PEI versus CEAT in group 2 and CEAT versus NT in group 3. The data were analyzed relative to 215 patients for 6 to 30 months. The Kaplan-Meier method was used to calculate survival rates, which were, at 24 and 30 months, 72% and 72% for PEI and 72% and 52% for CEAT in group 1, 52% and 28% for PEI and 70% and 50% for CEAT in group 2 and finally 30% and 20% for NT and 45% and 30% for CEAT in group 3. In group 1, PEI appeared markedly superior to CEAT. In group 2, the difference between PEI and CEAT was not statistically significant; the results in this group indicate that CEAT should be considered when three nodules are present because of PEI invasiveness in these cases. In group 3, CEAT results were definitely better in the first two years, but there was no difference with NT patients at the end of the third year. Therefore, CEAT is indicated in advanced HCC because it improves the survival rate in the first 24 months. After this period, the survival time is not modified by treatment.