Abstract: A manually operable resuscitator bag of one-piece construction having a generally elongated football shape, an inlet at one said end, and an outlet at the other end, fold-rings in each end portion having walls of reduced thickness, whereby the ends may be telescoped, ridges of thickened wall section between the fold-rings, the center of the bag having a wall thickness equal to the thickness of said ridges in the tapering ends between the fold-rings, and longitudinal ribs formed on the outer surface of the center of the bag spaced around the circumference, providing increased resiliency and a rapid recovery for the shape of the bag.