Neuroblastoma (NB), one of the most common solid tumors among children, is histologically classified by the degree of maturation. To elucidate the mechanisms underlying its maturational sequence, we analyzed gene-expression profiles of 14 NB tumors on cDNA microarrays consisting of 23,040 genes. Computational analysis identified 78 genes whose expression levels were significantly different between differentiating NB tumors and poorly differentiated NB tumors. This group included genes associated with cell maturation and apoptosis. Among them we identified 15 that were up-regulated in Stage IV NB tumors; these included genes encoding cell adhesion molecules and cytoskeleton proteins. The set of genes we report here should contribute to a better understanding of NB tumor maturation and could lead to development of new therapeutic strategies.