Dasatinib (Sprycel, Bristol-Myers Squibb) is a second-generation tyrosine kinase inhibitor (TKI). It is used in the treatment of chronic myeloid leukaemia (CML) 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 dasatinib may help in assessing adherence and in optimising treatment. A target range for plasma dasatinib during effective therapy has not been established as yet. However, in patients (N = 33) prescribed (median, range) 100 (50-150) mg/d dasatinib for CML the median (range) pre-dose plasma dasatinib concentration was 13 (2-143) µg/L.