Neuroblastomas, the most common extracranial solid tumors in children, present an extremely heterogeneous behaviour that can be explained in part by their genetic abnormalities. Thirty-four patients treated at the Pediatric Oncology Unit, Hospital Vall d'Hebron from 1993 to 1997 were prospectively studied to determine the relative prognostic impact of a number of clinical and molecular factors. The factors studied were: ploidy, MYCN and 1p status, and TRK-A expression, in addition to age, stage and histology. Their impact on prognosis was analyzed. In univariate analysis, advanced stage, unfavorable histology, diploidy, MYCN amplification, and 1p deletion were identified as adverse prognostic factors; TRK-A expression was associated with favorable prognosis. After multivariate analysis, only MYCN amplification proved to be an independent adverse prognostic factor (p=0.03), whereas TRK-A expression identified a subset of good-prognosis patients (p=0.003).