Neuroblastoma is perhaps the most heterogeneous childhood cancer in terms of clinical behavior. Stage of disease, age at diagnosis, levels of urinary catecholamine excretion, N-myc amplification, and DNA ploidy have been found to be significant prognostic factors. The aims of this combined retrospective-prospective study are to verify the prognostic significance of DNA ploidy and to show its correlation with other prognostic signs. Thirty six fresh and thirty three paraffin embedded samples from patients with histologically confirmed neuroblastoma (41 prior to receiving any chemotherapy) were available for flow cytometry DNA analysis. Our results showed that the maturation induced during chemotherapy could give rise to aneuploidy therefore we analyzed the associations between the DNA ploidy and other prognostic markers only in patients examined before chemotherapy. There were no significant correlations between DNA ploidy and urinary catecholamine metabolites levels or tumor localization. DNA aneuploidy was significantly more frequent in patients with lower clinical stage, lower age at diagnosis, and without N-myc gene amplification. Patients with DNA aneuploid neuroblastomas died less frequently than patients with DNA diploid tumors. There were no significant associations among the S-phase or proliferation fraction and other prognostic factors.