Frequency of BCR-ABL–negative and BCR-ABL–positive CFUs at diagnosis and during MMR. BCR-ABL–specific real-time PCR from individual CFUs was performed to identify the frequency of BCR-ABL–positive versus normal (BCR-ABL–negative) CFUs at the time of CML-Dx and MMR. (A) The sum of BCR-ABL–positive and normal CFUs is illustrated by dark versus gray bars, respectively. (B) The amount of BCR-ABL–positive and normal CFUs is shown for each patient individually. (C) The number of BCR-ABL–positive and normal CFUs is depicted depending on the indicated bone marrow compartment.