UNLABELLED: Chemotherapy regimes in children with cancer often cause gastrointestinal side effects. Only limited data exist on the use of endoscopy in this group of patients. METHODS: Retrospective review over a time period of 8.5 years identified 57 endoscopies (49 upper endoscopies, four colonoscopies, three sigmoidoscopies, one rectoscopy) in 38 patients (mean age 12.8 years). Seventeen children (45%) had hematological malignancies and 21 (55%) had solid tumors. In 12 children, platelet count was <50 × 10(9)/L and 10 children were neutropenic (ANC < 1 × 10(9)/L; absolute neutrophil count). RESULTS: Forty diagnostic endoscopies, seven follow-up endoscopies, and 10 therapeutic endoscopies were performed. Biopsies were taken in 30 (75%) of 40 diagnostic endoscopies and microbiology samples in 17 (42.5%). Pathological findings identified in 33 (82.5%) diagnostic endoscopies: esophagitis 15 (37.5%)-two of them infections: 1 candida, 1 HSV (herpes simplex virus); Mallory-Weiss tears 5 (12.5%); gastritis 18 (45%; four Helicobacter pylori positive); ulcer 1 (2.5%); duodenitis 11 (27.5%); neoplasia 3 (7.5%); and colitis 5 (12.5%). Therapeutic endoscopies: Four PEG (percutaneous endoscopic gastrostomy) tube placements, one tube removal, two sclerotherapies for esophageal varices, three nasojejunal tubes for enteral nutrition (EN), and three additional tubes in primary diagnostic endoscopies. COMPLICATIONS: One episode of fever (>38.5°C) after colonoscopy, one localized infection after PEG tube placement, and two episodes of temporary desaturation. No association of neutropenia with more infections was observed. No bleeding in thrombocytopenic patients was observed. CONCLUSION: The data show that endoscopy in high-risk pediatric patients with malignant diseases is a safe procedure. Endoscopy reveals relevant information and have therapeutic impact with high probability. Tube placement techniques can help to maintain EN.