We previously demonstrated the efficacy of a genetically engineered vaccine composed of syngeneic tumor cells mixed with syngeneic, IL-2 gene transduced fibroblasts in the CT-26 model of murine colorectal carcinoma. In this report, we describe a more practical approach to fibroblast mediated IL-2 gene therapy that employs syngeneic tumor cells mixed with allogeneic, IL-2 gene transduced fibroblasts. BALB/c mice were challenged with an injection of CT-26, 14 days following immunization with IL-2 modified syngeneic BALB/c 3T3 (H-2(d)) or allogeneic C3H 3T3 (H-2(k)) fibroblasts mixed with irradiated CT-26. Both syngeneic and allogeneic IL-2 modified fibroblasts provided significantly better protection compared to animals treated with control fibroblasts (syngeneic IL-2 fibroblasts 32/40-80% vs. control 15/45-33%, p<0.01; allogeneic IL-2 fibroblasts 25/37-68% vs. control 15/45-3345, p<0.01). There was no statistically significant difference between the groups immunized with syngeneic or allogeneic IL-2 modified fibroblasts. These findings support the evaluation of allogeneic IL-2 modified fibroblasts as a practical form of cytokine gene therapy for cancer.