Cell constituents of glomerular crescents still remain controversial. We examined cellular crescents in ten cases of crescentic glomerulonephritis (GN) using indirect immunoperoxidase technique and monoclonal antibodies against T cells (OKT3) and subsets: T helper/inducer cell (T4), T suppressor/cytotoxic cell (OKT8), T activated cell (IoT14 and IoT15); B cells (B1, B4, OKB2 and IoB3) and subsets (B2 and IoB1); monocytes/macrophages (LeuM3); DR Ag (I2) and renal native cells: podocytes (IoT5), Bowman's capsule (BC) parietal epithelial cell (OKB2, IoB3). Studied cases were 2 anti-glomerular basement membrane (GBM) GN, 4 immune complex GN, 3 vasculitis and 1 idiopathic GN. When the BC continuity was preserved almost all crescent cells were identified; they originated in majority from the BC parietal epithelium and ranged from 55 to 95 per cent. The other main constituents which represented 15 to 35 per cent of the crescent cells were monocytes (LeuM3+) and T-activated cells (IoT15+). In the interstitial infiltrate, which was mostly periglomerular, LeuM3+ cells and IoT15+ cells accounted for more than 70 per cent of the cell population. On the other hand, when BC were ruptured, mononuclear inflammatory cells, mainly LeuM3+ and IoT15+ cells accompanied by significant number of T4+ and T8+ cells, constituted the glomerular crescents. At this time, BC parietal epithelial cells were rarely identified (15 per cent). These findings strongly support the importance of BC integrity to discriminate the nature of crescent cells.