This work reports on a female patient with acute myelogenous leukemia (AML) FAB M 5a with initial extramedullary leukemia (EML) in skin, breast, and synovia. A year after diagnosis she developed a histologically proven isolated recurrence of the EML in the right upper ankle. The bone marrow was still in complete remission. Conventional x-ray, magnetic resonance imaging (MRI), bone scintigraphy, and 2-deoxy-2-[18F]-fluoro-D-glucose whole-body positron emission tomography (FDG-PET) were performed. All images showed alterations in the lower leg. Shortly after, an isolated relapse of the AML was diagnosed in the right elbow. FDG-PET demonstrated this lesion as well as an unknown lesion in the subcutis due to EML. In the course of her illness, the patient underwent one more PET examination for therapy control. The present observations suggest that whole-body FDG-PET may be valuable for the detection of EML and for the assessment of chemotherapeutic effects on identified lesions.