Second malignancies occur with a greater frequency in patients with chronic lymphatic leukemia than in the general population. Previously, 20 patients having CLL have been reported as developing acute leukemia, but no cases of development of chronic granulocytic leukemia have been observed. In the present report, we will describe patients with Ph1 chromosome positive CGL associated with previously described CLL. One patient received total body radiation treatment for his CLL, while the second was not treated. It is apparent that previous therapy may not necessarily be a prerequisite for the development of a second malignancy in CLL. Cytogenetics offers a useful tool to confirm morphologic criteria in establishing the diagnosis of a second neoplasm.