To validate sensitive neuroblastoma mRNA RT-qPCR BM testing, we prospectively assessed serial BM samples from 345 international high‐risk neuroblastoma patients, treated in trials NB2004 (GPOH) or NBL2009 (DCOG), using PHOX2B, TH, DDC, CHRNA3, and GAP43 RT-qPCR mRNA markers and BM GD2-immunocytology. The gene discussed is GAP43; the disease is neuroblastoma.