Abstract: An improved inflatable warning sign having a flashing light contained within the sign and a magnetic base to retain the sign to the roof or truck lid of a disabled vehicle. The sign as inflated is a prismatic triangele to maximize the visible rectangular area for lettering and minimize the wind resistance.In the preferred embodiment the light within the sign is red and the inflated bag is white with black lettering. The white bag disperses the red light within evenly, thus permitting much more effective use of a single incandescent bulb within a translucent red covered box. Deflated, a sign with an inflated lettering area of 8 by 17 inches folds into a package or pouch that easily fits within the glove box of an automobile.