An aspect of our work with quinoxaline 1, Cdioxides involved the synthesis and reactivity of (quinoxalin-2-y1) acrylonitrile 1, 4-dioxide. We have found that treatment of a methanolic solution of this unsaturated nitrile (cis or trans) with primary alkylamines affords a novel series of pyrido [2, 3-b] quinoxaline 5-oxides. These tricyclic pyridoquinoxalines represent a unique class of agents with oral activity against trichomoniasis.