An increasing number of cases of abdominal angiostrongyliasis have recently been diagnosed in southern Brazil. A comparative study of 19 confirmed cases and 15 suspected cases was undertaken to review the anatomo-pathology of the disease and to establish histopathological criteria for its diagnosis. The results were similar in both groups, except for the identification of the worm in the confirmed cases. Macroscopic features comprised two types: a predominant thickening of the intestinal wall (pseudo-neoplastic pattern) and a congestive necrotic lesion (ischemic-congestive pattern). Microscopically, three fundamental histopathological findings were detected: (1) a massive infiltration of eosinophils in all layers of the intestinal wall, (2) a granulomatous reaction and (3) eosinophilic vasculitis affecting arteries, veins, lymphatics and capillaries. We conclude that observation of this histopathological triplet excludes other causes of "eosinophilic gastroenteritis" and establishes the diagnosis of probable abdominal angiostrongyliasis.