The results are available of combined examination of the kidneys in 84 patients with manifest nephrotic syndrome varying in etiology: 57 had glomerulonephritis, 18 amyloidosis, 9 diabetic nephropathy. The study covered lipid metabolism, immunological status, lifetime morphological investigation of the kidneys. The latter procedure proved advantageous over biochemical and immunological studies in deciding upon nosological diagnosis of nephrotic syndrome and its prognosis. Destruction of podocytic miner processes revealed in all the syndrome cases can serve a uniform morphological substrate underlying massive proteinuria.