Abstract: In our previous work we found that some α-bromomethylketones inhibit influenza virus in vitro. This fact led us to sythesize a number of aromatic and aliphatic bromomethylketones(I). Furthermore Cavallini reported that 4-biphenyl-glyoxal (II, R=p-C₆H₅) is less effective in antiviral activity than its condensation product with paminobenzoic acid (III, R =p-C₆H₅,Xenalamine). Thus we also prepared certain known mono substituted phenyl glyoxals(II) which were reported to show antiviral activity against influenza virus in chick embryo, and also their condensation products of p-aminobenzoic acid(III) in order to find more effective antiviral agents as well as to compare their biological activities. All of the compounds, save a skin irritant, I_f, were tested against influenza virus in chick chorio-allantoic membrane of tissue cultures. With the exception of I_j, the other compounds are active under the test condition.