Preliminary studies of cis-regulatory elements are frequently performed in transiently transfected cells before further analysis in stably transfected cell lines and transgenic mice. However, not all cells are readily transfectable by routine means. For instance, mouse erythroleukemia (MEL) cells have been a valuable model system for studies of their endogenous globin genes, but introduction of DNA using common transfection methods such as electroporation has been very inefficient. This has allowed studies of stably transfected cells, after selection for the rare transfection events, but transient transfection analysis has been problematic. This report describes an efficient and reliable method for transient transfection of MEL cells using commercially available cationic lipids.