The overall aim is to monitor the quality of childhood cancer care in Denmark; to register late effects of treatment; to analyze complications of permanent central venous catheters (CVCs); to study blood stream infections in children with cancer; and to study acute toxicity of high-dose methotrexate infusions in children with leukemia.All children below 15 years of age at diagnosis living in Denmark diagnosed after January 1, 1985 according to the International Classification of Diseases 10, including diagnoses DC00-DD48.Cancer type, extent of disease, treatment, participation in international studies, recurrence of malignant disease, survival, yearly follow-up status, causes of death, and development of secondary malignancies. Type of CVC, causes for removal of the CVC, type of blood stream infection, pathogens isolated, antimicrobial sensitivity, and outcome of antimicrobial chemotherapy.Since 1985, 4,944 children below 15 years of age have been registered in the database. There has been no significant change in the incidence of childhood cancer in Denmark since 1985. The 5-year survival has increased significantly since 1985 and is now 86%. The median number of days from diagnosis to initiation of therapy is 7 days and in 80% of the children less than 14 days. Clinical data of 95% of the patients are reported to open international studies.The survival of Danish children with cancer since 2003 compares favorably with other international population-based studies. The annual reports support the collaboration within pediatric oncology in Denmark.