To study effects of a hammerhead ribozyme on chronic myelogenous leukemia (CML) cells and bone marrow purging in vitro, a bcr-abl specific ribozyme gene was introduced into CML and normal bone marrow cells using retroviral transduction. The effects of the ribozyme on primary cells from CML patients were detected by hematopoietic progenitor cell assays, flow cytometry and immunocytochemical methods. Then a model of remission was built up, and the effects of ribozyme on bone marrow purging were detected by leukemia colony assay and nest-PCR after transduction of this model by using the ribozyme. The results showed that ribozyme significantly suppressed the clonogenic growth and the expression of p210 protein in primary cells from CML patients, but did not affect the growth of normal hematopoietic progenitor cells. In the model of remission, ribozyme eliminated the proliferation and the expression of bcr-abl mRNA in residual K562 cells, but did not affect the expression of abl mRNA. The results suggest that anti-bcr-abl ribozyme might be used for bone marrow puring of CML cells.