A method of graded sieving for counting of glomeruli in removed kidneys is described. The number of nephrons (glomeruli) in six normal kidneys deriving from sutopsies of three children 22-73 months of age was 1.82 plus or minus 0.35 times 10-6. The results give a little higher number than most previous studies with which they are compared. In the kidneys of two 10- and 15-month-old patients with the congenital nephrotic syndrome of the Finnish type the mean number of nephrons was 3.17 plus or minus 0.52 times 10-6 which is on the average 73% higher than in the normal kidneys studied. The number of nephrons in kidneys of five other patients showed an average of at least 3.42 plus or minus 0.30 times 10-6 the counting method being a little different. The unusually high number of nephrons in CNF kidneys seems to be fully evident.