A series of 2-hydroxy-3-arylazo-1,4-naphthoquinones were prepared by coupling of 2-hydroxy1,4-naphthoquinone with aryldiazonium chlorides. The reactivity of the products toward electrophilic and nucleophilic agents was studied. In reaction with o-phenylenediamine they give condensation products, the corresponding benzo[a]phenazines.