Crescentic glomerular changes developed in goats 16 to 46 weeks after immunization with homologous or heterologous glomerular basement membrane (GBM) antigens incorporated in Freund's complete adjuvant. Mesangial widening, accumulation of migrant cells, fibrin deposition, and GBM thickening became manifest with time. The GBM was then attenuated and ruptured at a local area. Through the ruptured GBM, the influx of fibrin and blood cells occurred in the Bowman's space (BS) accompanying proliferation of epithelial cells lining the BS. The crescent thus formed was mainly composed of the capsular epithelial cells. The visceral epithelial cells (podocytes) and migrated blood cells contributed to the crescent formation to a lesser extent. Basement menbrane-like material appeared later between the crescentic cells and the crescent underwent a fibroepithelial form. The results indicate that the crescent develops in relation to the characteristic GBM damage with a resultant severe exudative change in the BS.