We used immunoelectron microscopy to examine whether glomerular podocytes have the endocytotic function of macromolecular proteins in the early stage of diabetic nephropathy. Diabetes was induced by injecting streptozocin 60 mg kg wt⁻¹ into rats. Creatinine clearance but not urinary protein excretion was increased after four weeks of diabetes. The kidneys were morphologically studied 1 h after goat serum injection. In conventional electron microscopy, lysosomes were conspicuous in the podocytes of diabetic rats. Immunoelectron microscopy revealed that endogenous rat IgG and exogenous goat IgG were present in the lysosomes of podocytes from diabetic rats. The results indicated that the podocytes had an increased capacity for endocytosis in the early stage of diabetic nephropathy without increased urinary protein excretion.