The direct introduction of an amino group into the purine moiety at positions N-1 and N-7 has been achieved in various purine nucleosides. This is the first reported direct amination of a purine ring nitrogen. Hydroxylamine-O-sulfonic acid converted inosine into 1-aminoinosine (2) and guanosine to 1-aminoguanosine (4). 6-Amino-9-β-D-ribofuranosyl-8-purinone (7) similarly gave 6,7-diamino-9-0-D-ribofuranosyl-8-purinone (8). A sequence of stepwise amination procedures with hydroxylamine-O-sulfonic acid provided direct introduction of the amino group at both positions N-1 and N-7 to give 1,2,7-triamino-9-β-D-ribofuranosyl-6,8-purinedione (12). These unique nucleoside derivatives provide interesting tools for future biochemical study. Since the N-amino group is capable of acting either as a hydrogen-bond acceptor or donor, these compounds at the nucleotide and polynucleotide level should present unusual possibilities for interaction with protein and nucleic acid. © 1969, American Chemical Society. All rights reserved.