DEAE-dextran transfection is one of the oldest chemical, nonviral methods developed to transfer RNA or DNA to cultured mammalian cells (1 ,2 ). Early transfection studies used viral RNA (1 ) and DNA (2 ), which were easy to propagate and purify, and allowed phenotypic discrimination of the transfected mammalian cells. The DEAE-dextran method is generally used only for transient expression studies, because long-term stable transfections are less successful using this reagent (3 ). The standard transfection protocol involves exposing the cells to a DEAE-dextran and DNA solution. An alternative procedure is to expose the cells first to DEAE-dextran, wash the cells, and then add DNA (4 ).