Pathologic study of an abdominal mass removed from a 16-month-old girl revealed a marked granulomatous and fibroblastic reaction surrounding eggs and adults of Ascaris lumbricoides. As often occurs in such cases, there was an increased eosinophilia in the lesion and in the peripheral leukocytes. Both the clinical and gross aspects of the lesion simulated a benign neoplasm; this similarity justifies the designation "pseudotumorous form of ascariasis".