1. The plain abdominal films of 246 cases of intussusception preceding hydrostatic barium enema were analysed in order to reassess the diagnostic reliability of the abdominal plain film examination. Then, these were compared with 42 cases in which the diagnosis had been rejected by means of barium enema. 2. It was found that diagnosis of the intussusception was possible in 80% of 246 cases on the basis of plain film findings alone. 3. The most common and reliable findings of intussusception in plain film diagnosis are those of sparse faecoloid bowel content and sparse amount of intestinal gas. 4. The loops of distended small bowel in cecal or ascending colon area and intraabdominal soft tissue mass are considered to be relatively reliable findings. 5. In 42 cases in which the diagnosis had been rejected by means of barium enema, intussusception was excluded in 74% of the cases on the bases of plain film findings alone.