[corrected] The megacolon is a frequent disease in our emergencie hospital, and approached in the urgency by your complications as fecal impaction, volvulus and perforations. The ulcerations in the megacolons contribute as probable sites of perforations To compare the frequencies of stercoral ulceration in Chagas' megacolon operated at urgency, by volvulus or fecal impaction, and electively, aiming at a better surgical conduct in the urgency surgery It was analyzed 356 anatomy-pathological exams from colon resection of operated patients due to Chagas' megacolon at urgency (102 cases; 29%) and electively (254 cases; 71%), from 1980 to 2000. The surgical urgency indications were attributed to volvulus (71 cases; 69,6%), fecal impaction (25 cases; 24,5%), perforated acute abdomen after rectal catheter or sigmoidoscopy (6 cases; 5,9%). The ulceration frequency was compared in both groups of resections, using chi-square The pathological anatomy - of surgery resection obtained at urgency surgeries, showed 26 cases of ulceration (25,5%) and in electively resections were verified 21 cases of ulceration (8,25%). The difference observed was statistically significant. The comparison among the groups of volvulus; fecal impaction and volvulus with fecal impaction, separately with electively surgery group evidenced significant differences in relation to volvulus and fecal impaction The higher frequency of ulcerations in the megacolon operated at urgency character emphasizes the needs of immediate resection of sigmoid colon, instead of conservative conduct of simple decompression colostomy, even in exploration laparotomy which the macroscopic examination of sigmoid does not show necrotic signs. This way, should prevent the occurrence of perforation in megacolon at mediate postoperative, with serious results.