Recently an amplification of NMYC oncogene was discovered in stage III and stage IV as well as in stage II neuroblastoma cells. The extent of NMYC amplification is of prognostic value. A high expression of NMYC on mRNA level is correlated to the NMYC gene-amplification. We utilized the in situ-hybridization technique for the detection of NMYC-mRNA expression on cellular level, and the Southern Blot method for analysing the total genomic DNA. In three stage IV patients with overt neuroblastoma in bone marrow cells, NMYC gene-amplification as well as NMYC-mRNA were detected. Seven control bone marrows of patients with different heamatological diseases in different stages did not contain positive cells in our in situ-hybridization assay.