PB1F2 is the 11th protein of the influenza A virus. The protein has variable sizes with truncations either at the C- or N-terminal ends. The most recent example being the 2009 pandemic H1N1 virus which codes for only 11 amino-acids of the C-terminus. A review of the reports since the discovery of PB1F2 in 2001 suggests a multifunctional role for this protein that includes a proapoptotic function in immune cells and an ability to cause increased pathogenesis in animal models by dysregulating cytokines and inducing inflammation. It has also been suggested that PB1F2 regulates polymerase activity via co-localization with PB1 and causes enhanced secondary bacterial pneumonia. This review primarily focuses on understanding the proapoptotic ability of PB1F2, its sub-cellular localization and the mechanism through which it brings about apoptosis. We believe there is much more to learn about PB1F2, as many of its proposed functions are strain, host or cell-line specific.