A total of 116 cases of intestinal eosinophilic granuloma caused by Angiostrongylus costaricensis in children were studied during the 10-year period 1966-1975 at Costa Rica's National Children's Hospital. A similar prevalence of cases was observed each year. The disease was twice as frequent in males as in females, and occurred predominantly in children 6-13 years old (53% of cases). The clinical symptoms were those of "acute abdomen," with pain at the right iliac fossa, pain on palpation, a tumor-like mass, abdominal rigidity, and painful rectal examination. The picture was, nevertheless, mild to moderate. Fever was classified as mild. Leukocytosis with predominance of eosinophils was seen in most cases. Radiology revealed rigidity and spasticity of the intestinal wall with poor filling on medium contrast. Thiabendazole and diethylcarbamazine were given, but there was no evidence that they were effective. Surgery was performed in 90 cases--appendectomy, ileo-colonic resection, or hemicolectomy. The main localizations of the lesions were the cecum, ascending colon, appendix, and small intestine. The pathologic findings in tissues were edema and rigidity of the intestinal wall, yellow granulations in the subsera and, in the later years of the study, eggs, larvae, or the parasite itself. Two of the patients died; the remainder recovered.