57 cases of intestinal oabstruction which were confirmed by operation and in which flat and uprig"nt abdominal films were obtained, were clinically and radiologically evaluated. L. In simple obstruction and strangulated obstruction, the duration of onset at admission is shorter and the abdominal pain severer in the latter. BP below the shock level and the increase of leukocyte above the 15, 000 are more prominent in the latter. 2. The cause of small bowel obstruction are as follows; the adhesion and band formation are most frequent, 66. 7% among which previous abdominal operations were experienced in 7g, 9;! And the incidence of occurrence of intestinal obstruction in g3, 3< within 2 years after thc* last operation, and the site of adhesion and band formation are most frequent in the ileum within 1m from the ileocecal valve and the incidence is 8Q 8,,. 3. The causes of strangulated obstr uction are as follows; adhesion, and kinking are .,>0; , volvulus 20pand internal herniation and constricted band formation 3Qp,. On the flat and upright abdomen,these findings are helpful for differentiation of strangulated obstruction from simple obstruction; closed loop is seen in the 38% of strangulated obstruction and in the ],Qy.' of simple obstruction, diminished gas pattern of small bowel in t'ne 33, 3;; of strangulated obtruction and in the 20% of simple obstruction, pseudotumor sign in the 20:,; of stragulated obstruction only, and the hepatic angle obliteration which is suggestive of ascites in the 71,4; of strangulated obstruction and the 35,5p; of simple obstruction. The above findings are more prominent in the strangulated obstruction than in the simple obstruction. The different air fluid levels in the gas distended small bowel loop is seen in the 1gp. Of the strangulated obstruction and in the 50. Ofo of simple obstruction, and widely arched gas distended loop in the 28, gp; of strangulated obstsuction and in the 45, Q of simple obstruction.