We herein describe the ultrasonographic findings of 19 patients with clinical suspicion of acute diverticulitis. The criteria considered as evidence of the disease included the identification of the diverticuli, thickening of the wall of the loop, alteration of local mesenterium and selective pain. Diagnosis was complemented by CT scan, barium enema and, in determined cases, colonoscopy. Of the 19 cases studied, 18 corresponded to acute diverticulitis of the sigma and one to acute salpingitis. The former 18 cases were correctly diagnosed by ultrasonography (uncomplicated diverticulitis) and the posterior CT scan did not provide additional information. In conclusion, ultrasonography is a highly sensitive and specific technique for the diagnosis of acute diverticulitis when the sigmoid colon is involved.