Nilotinib (Tasigna, Novartis) is a second-generation tyrosine kinase inhibitor (TKI), and is used in the treatment of chronic myeloid leukaemia (CML). It is used in patients who have primary resistance to imatinib, which may occur in 15-20 % of cases. Treatment failure has been attributed to poor adherence or inadequate dosage. Thus, monitoring plasma nilotinib may help in assessing adherence and in optimising treatment. A target range for plasma nilotinib during effective therapy has not been established as yet. However, in patients prescribed nilotinib for CML (400 mg twice daily, 15 d) the mean (SD) pre-dose plasma nilotinib concentration was 1.0 (+/- 0.5) mg/L.