Using a highly reproducible and robust cell-based HTS assay, the authors screened a 100,000 compound library at 14 and 114 μM compound concentration against influenza strain A/Udorn/72 (H3N2). The “hit” rates (>50% inhibition of the viral cytopathic effect) from the 14 and 114 μM screens were 0.022% and 0.38%, respectively. The hits were evaluated for their antiviral activity, cell toxicity and selectivity in dose response experiments. The screen at the lower concentration yielded three compounds, which displayed moderate activity (SI50 = 10-49). Intriguingly, the screen at the higher concentration revealed several additional hits. Two of these hits were highly active with an SI50 > 50. Time of addition experiments revealed one compound that inhibited early and four other compounds that inhibited late in the virus life cycle; suggesting they affect entry and replication, respectively. The active compounds represent several different classes of molecules such as carboxanilides, 1-benzoyl-3-arylthioureas, sulfonamides and benzothiazinones, which have not been previously identified as having anti-viral/anti-influenza activity.