We report the clinical features observed in 10 children, ranging from 5 1/12 to 13 7/12 years of age, with intestinal infections caused by Blastocystis hominis. A parasitological study of the stools was made by using the ethyl-acetate formol concentration technique and a count of the number of B. hominis per field was performed. In 8 of the cases, no other enteropathogens (viruses, bacteria or other parasites) were found, whereas in 2 cases Giardia lamblia was also isolated. Nine out of ten of the patients presented with abdominal pain. In three of the cases it appeared as a pseudo-appendicular ailment which led to an appendectomy. Those children who were treated with metronidazole and those who were not treated with antibiotic recovered satisfactorily.