Contamination of sequential PB collections with Ph-positive cells remains relatively constant. Marrow was obtained before priming and PB or BM were obtained after priming on protocols CY/GM/BM, MAC/G/PB, and CY/G/PB from patients with ECP or AP CML. On average, 20 metaphases from steady-state marrow, mobilized marrow, or PB collections were analyzed. Cytogenetic status of all collections are shown separately. In general, cytogenetic responses did not change significantly between the first and last PB collections. Marrow and PB cells were evaluated by metaphase analysis and/or FISH to detect the number of Ph-positive metaphases.