Radiolabelled meta-iodobenzylguanidine (mIBG) currently provides one of the most promising options for targeted radiotherapy of neuroblastoma. No means currently exists for prediction of mIBG uptake in tumour cells of individual patients other than semiquantitative inferences from diagnostic scanning which depend on the continued existence of a macroscopic tumour mass. A biological rapid assay which could be applied at initial biopsy would be invaluable in selecting patients for therapeutic strategies which incorporate radiolabelled mIBG. We have assessed the expression of the noradrenaline transporter gene in six human neuroblastoma cell lines and in three non-neural crest-derived cell lines using reverse transcription followed by the polymerase chain reaction. Transcription of this gene was observed in five out of six neuroblastoma cell lines but in none of the control cells. A highly significant correlation was established (P < 0.01) between gene expression and active cellular accumulation of mIBG. It is suggested that semiquantitative evaluation of noradrenaline transporter gene transcripts may be predictive of mIBG uptake by tumours in vivo.