Paget's disease of bone is a disorder of bone remodeling in which excessive production of structurally abnormal bone occurs, with the primary and fundamental abnormality residing in the osteoclast. To evaluate further the jeopardized bone marrow in Paget's disease, the authors studied 29 skeletal lesions by means of conventional bone imaging and antigranulocyte antibody bone marrow imaging in eight consecutive patients affected by Paget's disease. Bone scans showed abnormal tracer uptake in the 29 skeletal sites (11 pelves, 10 vertebrae, 5 extremities, 2 skulls, and 1 rib). Antigranulocyte antibody bone marrow scans showed decreased uptake of radiopharmaceutical in 16 (55%) of those 29 areas (8 pelves, 7 vertebrae, and 1 rib). Lesions appeared to be more extensive on bone scans than on bone marrow scans. It was concluded that antigranulocyte bone marrow scans may show focal defects in hematopoietic bone marrow in patients with Paget's disease. Paget's disease affects the cortical bone more severely than the bone marrow.