We studied the expression of the male-specific mH antigen H-Y on cultured human skin cells by investigating susceptibility to H-Y-specific cytolysis using conventional class I-restricted CTL clones in a modified cell-mediated cytotoxicity assay. In contrast to what was found in the rodent system, we observed H-Y-specific lysis of human male keratinocytes. Susceptibility for H-Y-specific lysis was efficiently enhanced by exposure of the keratinocytes to IFN-gamma. Our results demonstrate that human skin cells are equally sensitive for the activity of H-Y-specific CTLs as target cells of lymphoid origin. Finally, the cellular recognition of the H-Y mH antigen in the skin further supports its possible target function in the local graft versus host attack.