Summary. The hepatitis B virus (HBV) is frequently transmitted by sexual intercourse. Thus, HBV-guidelines recommend vaccination. However, we have identified healthy hepatitis B surface antigen and anti-HBc-negative unvaccinated sexual partners of patients with chronic hepatitis B. We investigated whether HBV-specific cellular immune responses were present that could explain the apparent protection against HBV infection. In six anti-HBc-negative HBV-exposed sexual partners, HBV-specific T-cell responses were studied by proliferation assay and cytometric bead array after stimulation with 74 overlapping peptides spanning the HBV core, pre-S and S-encoding regions. Eleven HBV-unexposed individuals served as negative controls. HBV-DNA was undetectable in serum and peripheral blood mononuclear cells in all cases. HBV-specific cytokine secretion was observed in 4/6 seronegative partners, but only in 1/11 controls. Proliferative responses were detectable in 5/6 partners and 0/11 controls. HBV-specific cytokine secretion exists in healthy seronegative virus-exposed individuals. HBV core-directed immune responses indicate past, but controlled viral replication. T-cell immunity may prevent clinical manifestation of HBV infection in the absence of humoral immunity.