Reproducible patterns of cell outgrowth have been observed from isolated normal adult, human glomeruli grown in tissue culture. Three morphologically distinct cell populations designated Types I, II, and III have been observed in culture from 15 normal human kidneys. Assessment of the morphology and behaviour of these cells has been made by phase contrast, time-lapse cinemicroscopic, transmission and scanning electron microscopic examination. The phagocytic capacity of these cells has been determined. The Type I cell appears in culture by migration from the capillary loops, its branched cytoplasm and ultrastructural features confirming its origin as a visceral epithelial cell. In keeping with the highly specialised nature of this cell, division was rare, movement was not observed, and differentiation was progressively lost in culture. The Type II cell was mobile and capable of active division. Ultrastructural features were those of mesangial cells. The Type III cell which was seen only rarely, had the features of a macrophage. Endothelial outgrowth was not observed.