Purpose and Methods: Based on preliminary expe-rience, there was a need for modifications and clarifications in the International Neuroblastoma Staging System (INSS) and International Neuroblastoma Response Criteria (INRC). In 1988, a proposal was made to establish an internationally accepted staging system for neuroblastoma, as well as consistent criteria for confirming the diagnosis and determining response to therapy (Brodeur GM, et al: J Clin Oncol 6: 1874-1881, 1988). A meeting was held to review experience with the INSS and INRC and to revise or clarify the language and intent of the originally proposed criteria. Substantial changes included a redefinition of the midline, restrictions on age and bone marrow involvement for stage 45, and the recommendation that meta-iodobenzylguanidine (MIBG) scanning be implemented for evaluating the extent of disease. Other modifications and clarifications of the INSS and INRC are presented. In addition, the criteria