The distribution of Fc-receptors for IgG (FcR) on human epidermal cells (EC) was characterized in situ using monoclonal antibodies (MoAbs) by indirect immunofluorescence staining of cryosections. The results showed heterogeneity of FcR expression on Langerhans' cells (LC) and keratinocytes (KC). The MoAb IV.3 against FcR II (CDw32) gave granular staining of most LC whereas the MoAb 32.2 against FcR I (CD64) occasionally stained a few dendritic cells. 32.2 demonstrated weak granular staining along the outer aspect of KC in stratum spinosum and stratum basale and intense staining of stratum corneum and stratum granulosum. The MoAbs Leu 11b against FcR III (CD16) and B1D6 reacting with a placental FcR with low affinity for IgG gave intense linear membrane staining of KC. Leu 11b produced strongest staining of stratum granulosum and B1D6 the strongest staining of stratum spinosum and basale. The results confirm our previous observations of FcR in situ on LC and KC in normal skin using functional assays and demonstrate that these EC possess different types of low affinity FcR. The data support the contention of an immune function of KC. FcR may be mediators for interaction between KC and LC. The FcR activity in stratum granulosum may have an immune function as a barrier against microorganisms and other antigens.