Objective. Hepatitis B virus (HBV) and HIV are endemic infections in many African countries. The objectives of this study were to determine the levels of exposure to, and protection from, HBV, as well as the prevalence of HIV/HBV co-infection and the response of HBV to highly active anti-retroviral therapy (HAART) in a cross-section of HIV-infected patients in north-eastern South Africa. Study design. This was a laboratory-based, unmatched study. Three hundred and eighty patients were screened by ELISA for HBsAg, anti-HBc and anti-HBs. Samples non-reactive for HBsAg but reactive for anti-HBc were examined for occult HBV infection. Response to HAART was assessed by measuring HBV viral loads, seroconversion from HBeAg to anti-HBe, and levels of aminotransferase. Results. Of the study population of 380, 60% (95% CI 54.8 - 64.9) were exposed to HBV based on HBsAg, anti-HBs or anti-HBc; 20% (95% CI 16.1 - 24.4) had active HBV infection, based on HBsAg serology, and 30% (95% CI 25.2 - 35.2) were protected, based on anti-HBs levels ≥10 IU/l. Of 181 HBsAg-negative individuals, 61 had HBV occult infection (33.7%, 95% CI 26.9 - 41.1). The differences in prevalence were not statistically significant when gender, marital status and CD4+ cell counts were considered. Of 21 patients analysed, 80% showed adequate response to the first-line HAART regimen (stavudine/lamivudine/efavirenz or nevirapine) after 12 months of use. Conclusion. The study confirms the higher level (60%) of exposure to HBV in HIV patients in Limpopo Province, as well as the high (20%) prevalence of HBsAg positivity and occult hepatitis B (33.7%). However, further studies are warranted to corroborate the benefit of lamivudine-containing HAART regimens, as HIV/HBV co-infected patients have a higher liver-related mortality if hepatitis B is not treated.