Stool specimens taken from 50 children with malignancy and from 92 healthy children were investigated for intestinal parasites, using the modified formol ethyl acetate concentration method, and native-lugol, trichrome and Kinyoun acid-fast stain methods. Thirty-eight (76.0%) of the 50 patients had lymphoma or leukemia and were considered immunosuppressed. Several different parasites were found in 21 (42.0%) of the 50 patients with malignancy and in 16 (47.3%) of the 38 patients with immune deficiency compared to in only 16 (17.3%) of the 92 healthy children. The incidence of parasites in patients with malignancy or immunosuppression was significantly higher than in the healthy control group (p<0.01, p<0.01).