Metabolically active and viable renal glomeruli were isolated from rats and piglets. In vitro, the glomeruli were active in protein and glycoprotein synthesis for at least 9 hr, as evidenced by linear incorporation of amino acids and carbohydrate precursors into macromolecules. Puromycin and cycloheximide inhibited the incorporation of labeled glucose, glucosamine, galac-tose and amino acids, while chloramphen-icol did not. After incorporation of labeled glucose and galactose, the products of the in vitro incubation were isolated and, labeled glucose and galactose were recovered from glomerular hydrolysates. This in vitro system is suitable to study the biochemistry of normal isolated rat glomuruli and can be adapted to other mammalian species. After basic information is gained on the biosynthesis of these isolated glomeruli, similar experiments may provide a better understanding of certain specific glomerular diseases in both experimental animal models and naturally occurring diseases of man.