Preclinical evaluation of a novel RNA interference technique has demonstrated that nanoparticles carrying small interfering RNAs (siRNAs) can penetrate glioblastoma multiforme (GBM) tumours and modulate the expression of oncogenes and apoptotic genes in mice. Effective targeting of GBM oncogenes by conventional methods is challenging, and the prognosis for GBM has remained poor. Jensen et al. found that systemic delivery of siRNA-conjugated nanoparticles reduced tumour burden without causing adverse effects in a mouse xenograft model of GBM.