Keratinocyte expression of the monocyte/macrophage surface antigens defined by OKM1 and OKM5 antibodies (Ortho Diagnostics) was examined using the peroxidase anti-peroxidase immunohistochemical technique. A range of inflammatory cutaneous disorders were investigated, including lichen planus, psoriasis and atopic dermatitis. Positive suprabasal keratinocyte expression of OKM5 antigen was observed in all disorders, while keratinocyte staining with OKMI antibody was consistently negative. These results provide further evidence that keratinocytes may play an important role in cutaneous immune responses. Furthermore, they are consistent with the recent observation that HLA-DR positive keratinocytes may modulate cutaneous immunological reactions by inducing T-cell unresponsiveness.