Influenza continues to be an important public health threat, and a need continues for models in which the disease, its prevention and treatment modalities can be studied. New colorimetric assay procedures, use of modified viral neuraminidase assays, branched DNA technology for quantifying the negative strand RNA of the viral gene, and polarity-specific viral RNA are among the in vitro assays considered. Studies in mice have focused on models of virus-induced encephalopathies, new disease parameters, and immunosuppression. Significant in vitro and in vivo models of influenza virus infection reported in the past two years are reviewed.