The synthesis of 6-(p-ethylphenyl)-5H-pyrrolo [3,4-b]pyridine-5,7-dione is described. The compound has been studied for its in vitro activity on RNA-containing influenza viruses types A and B. The preliminary results indicate that the compound has a significant antiviral activity against influenza viruses types A and B at concentrations at which no cytotoxic effects on MRC-5 cells in tissue culture are present.