Kinetic studies on the Hinsberg condensation were performed trying to improve yields and achieve regio-selectivity in the attainment of benzene-substituted 3-methylquinoxalin-2(1H)-ones. The course of the reactions between o-phenylenediamine (o-PDA) and substituted o-PDA with pyruvic acid ( 2a ) or ethyl pyruvate ( 2b ) were followed by uv spectrophotometry at different pH values. The formation of 3-methylquinoxalin-2(1H)-one ( 6a ) was improved using sulphuric acid-water mixtures, in which the reaction proceeded by a different mechanism. 3-Methyl-7-methoxyquinoxalin-2(1H)-one ( 7b ) was regioselectively synthesized independently of the pH of the reaction media. Reaction of 2-amino-4-methylamine ( 1c ) with 2a or 2b led to a mixture of 6 and 7-quinoxalinone isomers, 6c and 7c , while 2-amino-4-nitroaniline ( 1d ) and 2,4-diaminoaniline ( 1e ) with 2a or 2b did not afford the heterocycle. In every case reactions with 2a were 100–1000 times faster than those with 2b . Mechanisms are proposed trying to account for the experimental results.