To study aspects of glomerular cell response in varying types of glomerulonephritis, we evaluated isolated glomeruli from 101 normal and diseased adult human renal biopsy specimens in tissue culture. Glomerular cell outgrowths from normal glomeruli consisted of large stellate cells (type I) and smaller fusiform cells (type II). A very occasional cell (type III), which had the features of a macrophage, was seen. The cellular outgrowth from isolated glomeruli reflected the numbers and types of cells present in the diseased glomeruli. Reduced numbers of cells were found in the outgrowth of sclerotic, hypocellular glomeruli. Glomeruli from biopsy specimens with altered morphologic appearances but no increase in cellularity (minimal change nephropathy, membranous nephropathy) produced the same growth pattern as from glomeruli isolated from normal kidneys. In mesangial proliferative nephritis, increased numbers of type II cells were detected in the outgrowth. Large numbers of macrophages were found in the glomerular outgrowth of patients with crescentic glomerulonephritis. Macrophages were absent when crescentic glomeruli were sclerosed, indicating the importance of macrophages in the acute hypercellular phase of crescent formation.