Neuroblastomas are heterogeneous tumors. Their clinical behavior varies from spontaneous regression to malignant progression. To investigate the cytogenetic heterogeneity of infantile neuroblastomas, we employed comparative genomic hybridization (CGH). To characterize chromosomal imbalances in 35 infantile neuroblastomas, we performed CGH and compared our results with those of other clinical and biological studies. The most frequent genetic imbalances were found in chromosome 17 (43%), including whole chromosome 17 gains in eight patients (23%) and 17q gains in seven patients (20%). A 1p loss and a 2p gain were detected in six patients each (17%). Losses of 11q and 14q were detected in two patients (6%) and one (3%) patient, respectively. The number of gains of 17q were significantly higher in DNA diploid tumors than in aneuploid tumors (P=0.006). Conversely, whole chromosome 17 gains were not found in DNA diploid tumors and/or MYCN amplification. Interestingly, nine of 17 tumors that were histologically evaluated showed a spontaneous regression and did not demonstrate any partial chromosomal abnormalities (i.e. 17q gain, 1p loss, 2p gain, 11q loss and 14q loss). These results suggest that a gene on chromosome 17q is associated with neuroblastoma progression. Finally, our observations indicate that the chromosomal imbalances observed in infantile neuroblastomas are different from those observed in older patients.