Serum hepatitis B virus (HBV) infection markers were studied in 272 patients with homozygous genetic haemochromatosis complicated (n = 33) or not (n = 239) with primary liver cancer (PLC). Controls consisted of 255 029 healthy blood donors from whom age- and sex-matched control groups were extracted for statistical evaluation using the Fisher exact test. In blood donors, HBsAg was positive in 0.075% of males and 0.04% of females. This population was not screened for anti-Hbs. Anti-Hbc alone (without HBsAg) was present in 3.7% of men and 1.8% of women. In patients with genetic haemochromatosis without liver cancer (183 males, 45.6 +/- 11.3 yrs and 56 women, 48 +/- 12.4 yrs), HBsAg was found in 1.1% of men and in none of the women. Anti-HBs was present in 7.3% of males and 1.8% of females. Anti-HBc alone was found in 13% of males (p less than 0.005 vs. controls) and 2.1% of females. From male patients with primary liver cancer complicating genetic haemochromatosis (32 males, 61.7 +/- 6.8 yrs and one female), 6.2% were HBsAg positive, 3.4% were anti-HBs positive and 16.6% anti-HBc positive (p = 0.05 vs. controls). No serum HBV marker was found in the woman. In conclusion, the prevalence of HBV infection markers--especially anti-HBc--is significantly increased in patients with genetic haemochromatosis complicated or not with primary liver cancer.