During therapy with imatinib (Gleevec), 20-30% of patients with CML in chronic phase develop grade > or =3 thrombocytopenia. This leads to treatment interruptions and dose reductions that result in a decreased probability of achieving a cytogenetic response. Interleukin-11 (oprelvekin) is a megakaryopoietic cytokine that reduces the incidence and severity of thrombocytopenia associated with chemotherapy. We report on the use of interleukin-11 in three CML patients with grade > or =3, imatinib-induced thrombocytopenia. In all three patients, interleukin-11 led to improved platelets, uninterrupted administration of imatinib and improved cytogenetic response. This observation suggests that interleukin-11 may be beneficial for patients with imatinib-induced thrombocytoepnia.