The polymerase chain reaction was used to search for hepatitis B virus (HBV)-DNA sequences in the sera of HBsAg-negative Senegalese patients suffering from liver cirrhosis or liver cancer. Amplified HBV-DNA sequences were detected by hybridization with a digoxigenin-labelled HBV-DNA probe. HBV-DNA was detected in 17% of HBsAg negative Senegalese subjects from the general population and in 44% and 58% of the patients suffering from cirrhosis or primary hepatocellular carcinoma (PHCC) respectively. In the control group, amplified HBV-DNA was detected in 25% of the subjects without HBsAg and anti-HBs antibodies, and in 6% of subjects positive for anti-HBs antibodies. This study confirmed the hypothesis that there is an etiologic link between HBV and PHCC in HBsAg-negative patients.