Distribution of glycoconjugates in different areas of the rat kidney was studied by light and electron microscopy using six different horseradish peroxidase-labeled lectins. Glomeruli and brush borders of the proximal tubules reacted differently to these lectins, which indicated differences in the carbohydrate compositions of those regions. The ascending limb of Henle's loop (ALH) had strong binding sites for peanut agglutinin (PNA) and soybean agglutinin (SBA). Dolichos biflorus agglutinin (DBA) did not stain the cells of ALH but did stain those of distal convoluted tubules (DCT). DBA is a good marker for distinguishing ALH from DCT. DBA, PNA, and SBA were also good markers of the collecting duct. Ricinus communis agglutinin (RCA-1) and wheat germ agglutinin (WGA) diffusely stained the various components of different parts of the kidney.