A sieving technique was used to isolate human glomeruli and to fractionate them by size in order to determine whether nondiabetic and diabetic glomeruli can be separated from one another on the basis of size and mass and to observe the effects of diabetes on the physical properties of glomeruli. The kidneys studied were from 5 diabetic patients and 5 nondiabetic controls that were age- and sex-matched. About 40% of the glomeruli in the samples of renal tissues were isolated for study. The preparations consisted of > 90% glomeruli, and > 90% of the glomeruli were isolated whole. The mean diameter of the diabetic glomeruli was 45% greater than that of nondiabetic glomeruli. The mean mass of the diabetic glomeruli was 2.5 times greater than the mean nondiabetic glomerular mass.