Serum lipoproteins of 25 patients with uncomplicated renal diseases were studied with polyacrylamide gel block electrophoresis. (1) In the nephrotic syndrome (or nephrotic phase of nephritis), marked increases of chylomicrons, pre-beta lipoprotein or beta lipoprotein and decreases of alpha lipoproteins were detected in the most of the patients. Qualitative change was also frequent as in the glomerulonephritis. (2) In the renovascular hypertension, metabolism of serum lipoproteins was involved also. The principal abnormality was in alpha lipoproteins including the lipid-loaded albumin. Marked increases of alpha lipoproteins, to the level equal to or more than beta lipoprotein, was detected in 2 of 3 patients studied in this period. Surgical correction of abnormal physiology had resulted in a return to a normal lipoprotein profile. (3) In the glomerulonephritis confirmed by biopsies, serum lipoprotein abnormalities were detected more frequently than in the reported past studies as analyzed with the method employed in this study. Qualitative as well as quantitative abnormalities were in beta lipoprotein and alpha lipoproteins in the early and middle phase of the disease process. Gross qualitative change occured frequently. Furthermore, lipoprotein abnormalities in renal diseases were reversible; i.e., when the disease had ameliorated or was corrected surgically, the lipoprotein profile returned to the normal or near-normal profile. In conclusion, the results of the present study indicated that serum lipoprotein disorders are involved in the disease process of three major clinical entities of the renal diseases.