Postoperative course is reported in 52 children with malignant tumors (neuroblastoma, Wilms-tumor, non-Hodgkin-lymphoma, osteosarcoma etc.) who were operated on between 1979 and 1987. 26 children received chemotherapy prior to surgery, whereas 26 children were operated on without preceding chemotherapy (control group). Most children were under six years of age. 15 Children (57.7%) with preoperative chemotherapy developed early postoperative complications, such as sepsis, pneumonia, suture dehiscence, woundhealing disturbances and ileus, whereas this was the case in only 5 children (19.2%) without preoperative chemotherapy (P 0.0005). Four of the children with preoperative chemotherapy (15.4%) sustained late complications, such as local recurrence or mechanical bowel obstruction, whereas none of the control children did so. Lethality rate from underlying disease did not differ in both groups during follow-up (5 = 19.2% vs. 5 = 19.2%). This demonstrates that the surgeon must carefully be aware of an increased possibility of early and late complications in children who have to undergo surgery for malignant tumors following preoperative chemotherapy.