Chimeric antigen receptor-modified T (CAR T) cells have shown efficacy in leukaemia and lymphoma. Now, O'Rourke et al. report on the first clinical trial of CAR T cells targeted to the epidermal growth factor receptor variant III (EGFRvIII) in 10 patients with recurrent glioblastoma. Treatment was well tolerated, and at day 28, nine subjects had stable disease, with one patient remaining stable for over 18 months of follow-up. Analysis of the seven patients undergoing post-CAR T EGFRvIII surgical intervention showed CAR T EGFRvIII trafficking to the tumour and a decrease in EGFRvIII target antigen expression.