Hepatocellular carcinoma (HCC) is the most frequent primary cancer of the liver and the most frequent tumour in males, worldwide. The annual incidence of HCC is maximum in Asian and African countries, lower in western countries where it is close to 4/100,000 inhabitants. In 90% of the cases, HCC complicates course of liver cirrhosis, with an annual incidence in cirrhoties of 2 to 6%. Risk factors for HCC in cirrhotics are male gender (sex-ratio: 4/1), age (above 50 years old), macronodular cirrhosis and large cell dysplasia. HCC can complicate the course of cirrhosis of any cause, but might be less frequent in primary biliary cirrhosis, Wilson's disease and auto-immune hepatitis. Currently, the diagnosis of HCC is usually considered in the presence of a focal nodular lesion, during systematic ultrasonographic examination of the liver. In high incidence areas, HCC can still be diagnosed because of HCC-related symptoms. In the case of a focal lesion discovered on a cirrhotic liver, the diagnosis of HCC can be confirmed by studying the behaviour of the lesion of helical CT scan of the liver (enhancement of the tumour during the arterial phase) or MRI (hyperintensity of the tumour on T2 relaxation time); study of peritumour vessels can also be helpful. Serum alpha-foeto-protein level, when higher than 300 to 500 micrograms/L is very specific of HCC. When aggressive treatment of HCC is considered and when the diagnosis of HCC remains uncertain, HCC can be assessed by means of cytological or histological study of the tumour on samples taken by fineneedle aspiration (80% sensitivity) or liver biopsy during laparoscopic laparotomy. Forthcoming improvements in imaging technology might eliminate the need for such invasive diagnostic techniques in the future.