Many studies have reported that neuroblastoma patients with aneuploid DNA content and a low cellular proliferative activity have better outcome; other studies have reported contradictory results. Formalin-fixed, paraffin-embedded archival pretreatment specimens of 56 neuroblastomas were studied. Thick sections from paraffin blocks were deparaffinized, and rehydrated. following enzymatic digestion and filtration, cellular suspensions were analyzed by flow cytometry. Six tumors were aneuploid (13.3%) and 39 samples were diploid (86.7%). S-phase fraction (SPF) ranged from 1 to 78% with a median of 31 %. DNA ploidy and proliferative activity results showed no correlation with the prognostic variables. There was no significant difference between the 5-year overall and event-free survival rates of the aneuploid and the diploid neuroblastomas or between the neuroblastomas with a high and low proliferative activity. The results revealed the prognostic significance of neither DNA ploidy nor the cellular proliferative activity in neuroblastoma In contrast to other studies.