Ben Hassine I, et al. – This study investigates whether genetic variations and/or altered expression of ABCB1 gene may influence response to imatinib. The 1236C–2677A–3435C haplotype has been observed only in imatinib non–responders’ patients. It suggests that CAC haplotype is linked to higher risk of imatinib resistance. On the basis of these outcomes, in order to study the relationship between ABCB1 genotypes and imatinib efficacy, analyses of ABCB1 haplotypes should be taken into account.