A multicomponent herbal formula Ledretan-96 was tested on an epithelial tissue culture cell line (MDCK) for its protective activity against cytopathic effects caused by influenza A virus. The whole formula and each of its 23 individual components were tested in the same system. The results indicated that the formula, when prepared according to established procedure, in the form of decoction, is active in protecting epithelial cells against damage caused by influenza A virus used at different dosages. Of the 23 components tested, only one, Terminalia chebula, showed a significant protective effect when applied to the epithelial cells individually. Controls for these studies included cell cultures exposed to individual components and the complete formula without virus; the cultures were monitored for any toxic effects by morphology and protein synthesis. The protective effects of Ledretan-96 and Terminalia chebula could be distinguished from toxicity against the epithelial cells. In addition, the results indicated that the complete formula maintained antiviral activity at a higher therapeutic index than the Terminalia chebula extract alone.