Fifteen cases (3.1%) of localized myeloblastic tumors occurring among 478 patients with acute granulocytic leukemia (AGL) and chronic granulocytic leukemia (CGL) are described. The majority of tumors were discovered at autopsy. Numerous cases of chloroma associated with AGL have been reported; however, in this series, the incidence of myeloblastic tumors in CGL was twice as high. The importance of employing histochemical methods for myeloperoxidase activity to identify myeloblastic tumors is pointed out. Experience in this group of cases confirm the frequent involvement of the ovary and the common localization of myeloblastic tumors to perineural and epidural structures. With CNS involvement by myeloblastic tumors, pain and compression symptoms may be effectively relieved by laminectomy and local x-ray therapy. After the appearance of a myelogenous tumor in CGL, the course of the disease is rapidly progressive.