Malignant cells often elude the immune system by lacking costimulatory signals required for the generation of effective antitumor immunity. Immunization with tumor cells genetically modified to express costimulatory molecules is a highly promising approach to cancer immunotherapy. However, genetic modification of tumor cells is not only labor/time intensive but is also less efficient and bears safety concerns. To override these complications, we have recently developed a novel technology that allows for efficient and durable display of exogenous proteins on the surface of a cell within 2 h. This technology involves modification of the cell membrane with a biotin derivative and decoration of biotinylated cells with proteins chimeric with core streptavidin. A chimeric molecule composed of the extracellular domains of the human CD80 costimulatory molecule and core streptavidin (CD80-SA) was efficiently displayed on the cell surface, where it persisted with a t(1/2) of >10 days in vivo. Tumors from patients with advanced stage gynecologic cancers decorated with CD80-SA elicited potent ex vivo tumor-specific proliferative and cytotoxic responses in autologous lymphocytes. Immunization with tumor cells decorated with CD80-SA completely prevented tumor growth in an aggressive model of mouse lymphoma. This technology may serve as a fast, efficient, and safe alternative to gene transfer approaches for engineering tumor cells for use in immunotherapy and research.