In this paper, we describe three cell types from the explanted human glomerulus: the circular glomerular cell (CGC), the rhomboid glomerular cell (RGC), and the small ovoid glomerular cell (SOGC). These cells were compared with subcultured human umbilical vein endothelial and smooth muscle cells, uterine smooth muscle cells, and skin fibroblasts. Immunochemical comparisons utilized antiserums to antigens in the human glomerulus: antiglomerular basement membrane, antifibroblast surface antigen (FSA) (reactive extensively with the mesangium), antiactomyosin (AMY) localizing more restrictively in the mesangium, and antihemophilic factor (AHF) localizing to the endothelium. No cultured glomerular cells bore the AHF marker of endothelial cells. The epithelioid CGC excrete most GBM antigen as an orderly palisade of granules from the cell surface. FSA is rapidly lost from the cell surface. RGC have a typical multilayered smooth muscle morphology and have a most prominent complex AMY pattern of periodic aggregates and fibrils. FSA adheres to the cell surface. SOGC form an initial nonoverlapped monolayer resembling endothelial cells but elongate and form multilayers after confluency. The AMY fibril pattern of SOGC is distinctively multidirectional. The translation of in vitro characteristics into in vivo identification must be interpreted cautiously: CGC may derive from glomerular epithelial cells; RGC may derive from mesangial cells; and SOGC may represent a more rapidly proliferating, less differentiated form of the epithelial cell or another, unidentified, glomerular cell type.