The use of antivirals to manage influenza requires, ideally, universal methods to determine the susceptibility of the virus. A cell-ELISA (cELISA)-based assay was developed and characterized. Influenza A viruses A/Chicken/Pennsylvania/21525/83 (H5N2), A/Chicken/Saudi-Arabia/569017/00 (H9N2), A/PR/8/34 (H1N1), and A/Netherlands/33/03 (H7N7) were used. The heterogeneous MDCK cell line was cloned and two clones best supporting virus spreading, MDCK-T CB4 and MDCK-I BD5, were selected. For amantadine, the 50% inhibitory concentrations (IC50s) were similar with both clones. The A/PR/8/34 virus was resistant for amantadine. The IC50s of the avian viruses and the A/Netherlands/33/03 virus for oseltamivir and zanamivir, using MDCK-T CB4 cells, roughly paralleled those estimated using a fetuin-based neuraminidase enzyme inhibition (NI) assay. IC50s could not be reliably measured using MDCK-I BD5 cells due to extensive neuraminidase-induced pileup of virus on the cells. In conclusion, our results suggest that the cELISA, using MDCK-T CB4 cells, can be universally used. However, since adjustment of the cELISA appeared to be virus- and cell-specific, this approach is only recommended in a research setting. Further studies should indicate which method best correlates with in vivo efficacy. [Copyright &y& Elsevier]