Polyclonal T-cells can be directed against cancer using transmembrane fusion molecules known as chimeric antigen receptors (CARs). Although preclinical studies have provided encouragement, pioneering clinical trials using CAR-based immunotherapy have been disappointing. Key obstacles are the need for robust expansion ex vivo followed by sustained survival of infused T-cells in patients. To address this, we have developed a system to achieve selective proliferation of CAR(+) T-cells using IL-4, a cytokine with several pathophysiologic and therapeutic links to cancer. A chimeric cytokine receptor (4alphabeta) was engineered by fusion of the IL-4 receptor alpha (IL-4Ralpha) ectodomain to the beta(c) subunit, used by IL-2 and IL-15. Addition of IL-4 to T-cells that express 4alphabeta resulted in STAT3/STAT5/ERK phosphorylation and exponential proliferation, mimicking the actions of IL-2. Using receptor-selective IL-4 muteins, partnering of 4alphabeta with gamma(c) was implicated in signal delivery. Next, human T-cells were engineered to co-express 4alphabeta with a CAR specific for tumor-associated MUC1. These T-cells exhibited an unprecedented capacity to elicit repeated destruction of MUC1-expressing tumor cultures and expanded through several logs in vitro. Despite prolonged culture in IL-4, T-cells retained specificity for target antigen, type 1 polarity, and cytokine dependence. Similar findings were observed using CARs directed against two additional tumor-associated targets, demonstrating generality of application. Furthermore, this system allows rapid ex vivo expansion and enrichment of engineered T-cells from small blood volumes, under GMP-compliant conditions. Together, these findings provide proof of principle for the development of IL-4-enhanced T-cell immunotherapy of cancer.