Recent studies have shown that structural abnormalities of chromosome 17 resulting in gain of material are the most frequent genetic changes in neuroblastoma. We have established a new neuroblastoma cell line from a patient whose disease had evolved from stage 4s to 4, without evidence of deletion of the short arm of chromosome 1 and MYCN amplification, which are considered the most typical genetic indicators of aggressive disease. The cytogenetic study allowed a full characterization of the chromosome changes, and revealed a complex translocation of chromosome 17 leading to a derivative marker which may be described as follows: der(11)t(11;17)(p15;q12)t(11;17) (q22;q12). This resulted in a gain of part of the long arms of chromosome 17, which was recently associated with poor prognosis.