Abstract The purpose of this study was to demonstrate the radiological features of long bones in synovitis, acne, pustulosis, hyperostosis, osteitis (SAPHO) syndrome and to correlate these with the clinical findings. Eleven long bone lesions in seven cases of SAPHO syndrome were examined. The patients ranged in age from 6 to 63 years, with a mean of 47 years. In all seven cases, radiography, (99m)technetium bone scintigraphy, CT scan, and magnetic resonance imaging (MRI) were performed. In six of the cases, bone biopsy and bone culture were carried out for 7 long bones. Seven of the involved lesions were from the shaft of the femur, one each was from the neck and the shaft of the humerus, and one was from the proximal tibia. These lesions showed radiologically hyperostosis, osteolysis, and bone infarction-like lesion. Osteolysis was occasionally accompanied by sclerotic change. Hyperostosis usually showed diaphyseal involvement, presenting low signal intensity on T1- and T2-weighted MR images. Histologically, these findings corresponded to massive bone necrosis, new bone formation, fibrosis, or a mixture of these associated with mild inflammatory cell infiltration. Osteolysis involved dyaphysis, metaphysis, or epiphysis associated with arthritis, and presented low signal intensity on T1-weighted images, nonhomogeneous signal intensity lower than fat on T2-weighted images, and high signal intensity on fat suppression images. These findings corresponded to fibrosis, granulation, and inflammatory cell infiltration with lymphocyte aggregation. Bone infarction-like lesion was observed in the shaft or neck of the femur and the humerus and accompanied by calcification and cystic change. Bone cultures were negative in all cases in which bone biopsy was performed. Although hyperostosis is thought to be a characteristic bone lesion in SAPHO syndrome, the long bone lesion can occasionally show not only hyperostosis but also osteolytsis and bone infarction-like lesions.