In an attempt to evaluate the real efficacy of loop colostomy for fecal diversion, the authors studied 62 patients previously colostomized under emergency conditions. Radiologic series of the abdomen were taken after 200 gm of barium meal. The results showed that the colostomy provided complete diversion of the radiologic contrast in 53 patients (85 percent) and incomplete diversion in nine patients (15 percent). Analysis of the results revealed that incomplete fecal diversion was: 1) observed as of the 86th postoperative day, with a significantly higher frequency following the 10th postoperative month, and 2) significantly correlated with either colostomy retraction or prolapse. The authors present a diagram showing a possible interaction of factors responsible for incomplete fecal diversion in loop colostomy and conclude that: 1) retraction is probably the basic contributing factor for colostomy failure; 2) the prolapse, once reduced, propitiates sinking of the stoma, facilitating colostomy failure; 3) the common assumption that loop colostomy eventually fails to provide complete fecal diversion is further supported; 4) loop colostomy assures, over its usual duration, a satisfactory defunctionalization of the colon; and 5) use of improved techniques of colostomy construction may prolong complete fecal diversion.