N-myc gene amplification is the most characteristic feature of neuroblastoma. c-myc oncogene, another member of myc gene family, plays an important role in cell proliferation and differentiation. Both of them may contribute to tumorigenesis of neuroblastoma. In this study we use the in situ hybridization and immunocytochemical methods to test the frequencies of N-myc and c-myc expressions in 20 cases of human neuroblastoma at mRNA and protein levels. The positive rates of the expression of N-myc are 90% and 100% detected by in situ hybridization and immunocytochemical methods respectively. The positive rates of c-myc are 80% and 85% respectively. Sixty percent of the 20 specimens tested by in situ hybridization and 55% by immunocytochemistry show an inverse relationship between the expressions of these two oncogenes and this may indicate that there are different gene expression controlling mechanisms in different cases.