According to the present invention, there is provided a pharmaceutical composition for treating Philadelphia chromosome positive lymphocytic leukemia, including a thalidomide derivative and BCR-ABL tyrosine kinase inhibitor. According to the present invention there is also provided a method of treating Philadelphia chromosome positive lymphocytic leukemia, including administering a thalidomide derivative and a BCR-ABL tyrosine kinase inhibitor to a patient suffering from Philadelphia chromosome positive lymphocytic leukemia.