Over a four-year period 40 patients of local origin, with primary hepatocellular carcinoma were seen at a regional referral centre. Twenty-nine patients had histological evidence of underlying cirrhosis and these patients were predominantly male (25/29) and elderly (mean age 66 years). Serological evidence of hepatitis B virus (HBV) infection was found in 11 (38 per cent) of the cirrhotic group. Of the 25 males with cirrhosis, 13 (52 per cent) were known to have seen military service in the tropics and of these eight had serum HBV markers. The non-cirrhotic group was younger (mean age 55 years) and the sex distribution was nearly equal (six male, five female). Two patients (19 per cent) had hepatitis B markers including one of the two men in this group who had served in the tropics. One patient with no serum HBV markers had integrated HBV-DNA sequences in the cellular DNA of her tumour. These observations confirm the association of primary hepatocellular carcinoma with hepatitis B virus and suggest that a significant proportion of patients of United Kingdom origin acquired their susceptibility as a result of military service in the tropics. There is presumably a substantial cohort of ex-service men at risk of developing primary hepatocellular carcinoma.