In a case-control study, 62 Somali patients with chronic liver disease (CLD) including primary hepatocellular carcinoma (HCC) and the same number of age and sex matched controls were investigated for serological markers of hepatitis C virus (HCV) and hepatitis B virus (HBV) infections. Antibody to HCV (anti-HCV) was detected in 40.3% and 6.5% of cases and controls, respectively. The corresponding prevalences of hepatitis B surface antigen (HBsAg) were 37.1% and 9.7%, respectively. Of the HBsAg-positive cases, 34.6% had antibodies to hepatitis D virus (anti-HD) compared with 14.3% among the HBsAg-positive controls. Anti-HCV was less prevalent in HBsAg-positive cases than among HBsAg-negative patients (p < 0.001), indicating that these agents were independent causes of CLD/HCC. The odds ratios for patients with CLD/HCC associated with the presence of anti-HCV, anti-HD, HBsAg without anti-HD and anti-HCV, were found to be 9.8, 10.4, and 3.3, respectively. When the patients were divided into tumour and non-tumour cases, using the criteria of serum alpha-fetoprotein > 100 ng/ml and/or solid hepatic lesions detected by ultrasonography, they did not differ with regard to frequencies of HBsAg and/or anti-HCV, although they did differ when these markers were taken together (43/49 versus 5/13, respectively). The mean age of the tumour patients with anti-HCV alone was significantly higher than that of tumour patients with HBsAg as the sole marker, 61.7 versus 31.4 years (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)