Disseminating disease in neuroblastoma is of considerable clinical importance. Detection of circulating neuroblastoma cells using tyrosine hydroxylase (TH) as a tissue-specific target for reverse transcriptase-polymerase chain reaction has proved to be a sensitive and specific method for the detection of contaminating tumour cells in peripheral blood. The aim of this study was to report the early clinical observations made using this technology in neuroblastoma patient blood samples. A strong association was found between the detection of neuroblastoma cells in circulation with the detection of neuroblastoma in bone marrow. This method may be of use to monitor disease status and identify early signs of relapse in clinically disease-free patients. These results show that RT-PCR detection of TH mRNA is a relatively noninvasive, sensitive method for the detection of circulating tumour cells in neuroblastoma patients.