Although other groups have demonstrated the feasibility of detecting BRAF mutations in serum and plasma of patients with melanoma (Daniotti et al, 2007; Shinozaki et al, 2007; Yancovitz et al, 2007), this is the first study that compares tumour and cfDNA results from a large cohort of patients and demonstrates the potential clinical application of cfDNA mutation detection for patient selection within clinical trials. The gene discussed is BRAF; the disease is melanoma.