Cytokine gene transfer is a current approach in studies of gene therapy of cancer IFNs represent valuable cytokines for these studies, since they exert multiple biological effects, including anti-tumor activities. Early studies have been focused on IFN-gamma. Recently, several reports have shown that the transfer of type I IFN (especially IFN-alpha) genes represents a powerful approach for inducing tumor suppression. Recent studies have underscored new IFN-induced activities on immune cells. This knowledge adds a further rationale for the use of IFN-alpha in strategies of gene therapy of cancer and can be exploited for the design of more selective and effective anticancer treatments.