The synthesis of ureides was studied in root, stem, and leaf tissues, as well as in intact seedlings, of silver maple (Acer saccharinumL.) using radiotracer techniques. Ureide synthesis was demonstrated from carbon-14 labeled adenine, glycine, formate, urea, and bicarbonate. Ureide synthesis from adenine apparently followed the degradative pathways previously known in animal tissues. Synthesis of ureides from glycine, formate, urea, and bicarbonate appeared to be via a purine precursor, probably inosinic acid or a closely related compound. The experimental methods were not discriminating enough to demonstrate whether ureides are normally synthesized in the roots and translocated to the tops of maple seedlings.