Following busulfan induced bone marrow insufficiency, a patient witha chronic granulocytic leukemia (CGL) has had a survival lasting 18.5 years. During remission, chromosome studies on bone marrow have not shown Philadelphia chromosome (Ph 1). There was no correlation between this observation and initial pronostic factors from literature. Analysis of 14 cases (13 from literature) of prolonged survival showed that Ph 1 was absent in 4 cases when only 15% of CGL are initially Ph 1 negative. Therapeuticcaryoconversions were probable. Recently attempts have been made to eradicate the abnormal Ph 1 positive clone. Some hopeful results are reported.