1. Conditions favouring the condensation of o-phenylenediamine with alpha-oxo acids to form substituted quinoxalines have been investigated. The best yields (85-100%) are obtained by incubation of the reagents in 2m-hydrochloric acid. Substitution of acetic acid for hydrochloric acid, or of halogen-substituted 1,2-diaminobenzenes for phenylenediamine, increases the initial rate of reaction, but...