This multicentre study focused on monitoring imatinib mesylate (IMA) trough plasma (Ctrough) and intracellular (IMA Cintrac) concentrations in 228 chronic myelogenous leukaemia patients. The median of measured IMA Ctrough in our patient group was 905.8 ng ml (range: 27.7–4628.1 ng/ml). We found a correlation between IMA Ctrough and alpha 1-acid glycoprotein plasma concentrations (rS = 0.42; p < 0.001). All other analysed parameters revealed only weak (gender, dose of IMA per kg) or not significant (age, albumin, creatinine plasma concentration or body mass index) impact on measured IMA Ctrough. The IMA Ctrough decreased during the first 6 months and significantly increased later during treatment. The IMA Ctrough at the first month of therapy did not differ between patients with and without an optimal response at the 12th (p = 0.724) and 18th month (p = 0.135) of therapy. There were no significant differences in medians of IMA Ctrough between both groups measured during the first year of treatment. The IMA Cintrac during the first month were not different between patients with and without an optimal response at the 6th (p = 0.273) and the 12th month (p = 0.193) of therapy. Our data obtained from real life clinical practice did not find a benefit of routine and regular IMA Ctrough nor IMA Cintrac therapeutic drug monitoring in chronic myelogenous leukaemia patients or for subsequent adjustments of the IMA dose based on these results. Moreover, actual alpha 1-acid glycoprotein plasma concentration should be used for proper interpretation of IMA Ctrough results. Copyright © 2013 John Wiley & Sons, Ltd.