IgG Fc receptors (FcR) in cryostat sections of human kidney were studied using functional assays and monoclonal antibodies (MoAbs). Using functional assays, FcR were detected on cells in glomeruli and distal convoluted tubuli, on endothelial cells and on interstitial cells. These cells were also stained with B1D6, a MoAb reactive with a 40-kD molecule with low affinity FcR activity. Using MoAbs against leukocyte FcR, a different pattern of reactivity was obtained. MoAbs against FcR I (32.2), FcR II (IV.3 and C1KM5) and FcR III (3G8 and Leullb) stained interstitial macrophages only. The data confirm the presence of FcR on renal glomeruli and interstitial cells and also indicate that epithelial cells of distal tubuli and endothelial cells express FcR. Furthermore, renal FcR appear to be structurally different from the FcR I, II and III defined on leukocytes.