THE POPULARITY of the air contrast barium enema depends on two asserted reasons: (1) its ability to detect polyps that can be discovered by no other method and (2) the clarity of studies which result. When this method was used to the exclusion of others several serious mistakes caused us to question its worth. We recall other air contrast studies, such as air myelography, air hysterosalpingography, and air arthrography, that were at first enthusiastically accepted and later abandoned. We believe that perhaps this should be the fate of the air contrast barium enema. Numerous problems arise when the air contrast method is used. The most important of these are superimposition of redundant, distended loops of bowel, which causes confusing shadows; sessile lesions (which are the important ones) not adequately demonstrated; numerous artefacts and the attempt, by repetition of the study to tell true from false lesions. These problems are for