The purpose of this paper is to provide a general survey of the GEM (ground effect machine) or air-cushion vehicle as it is sometimes called. Some concepts, accomplishments, and some of the problems which must be solved are reviewed. Lifting power requirements of the annular jet concept are defined along with effects of geometry on power requirements. Propulsion, stability, and control aspects are summarized. Two design studies are presented and used in an operational analysis which compares the air-cushion vehicle operating costs with those of existing transport media.