The cellular composition of crescents in diffuse crescentic glomerulonephritis is still controversial. Ten renal biopsies were studied on serial sections by using antikeratin antibodies as specific markers of epithelial cells of Bowman's capsule and both anti-macrophage and anti-lymphocyte antibodies. Semiautomatic morphometry showed that cellular crescents consisted of epithelial cells of Bowman's capsule (24-61%), of macrophages (19-34%) and of unlabelled cells (12-53%). In each biopsy, parietal epithelial cells outnumbered macrophages within crescents.