Disseminated atypical mycobacterial infection has been reported mainly in patients with AIDS and hairy cell leukemia. We describe three patients with chronic myelogenous leukemia (CML) who developed disseminated atypical mycobacterial infection in the chronic stage of their disease. The incidence of the latter infection is 3.9% among patients with CML at our institution; such a high incidence has never before been reported. There are no specific signs or symptoms other than fever. The bone marrow is the culture site most often useful in diagnosis. An immunologic defect may be one of the features of CML. Clinicians must thus be aware of the possibility of disseminated atypical mycobacterial infection in patients with CML.