Plasma-cell osteomyelitis is a histological diagnosis and, in the opinion of some authors, is a disease entity which can be differentiated from the sclerosing osteomyelitis of Garré and Brodie's abscess. Our investigation of 12 patients with plasma-cell osteomyelitis leads us to a different conclusion. The radiological appearances are not specific and do not allow a definitive diagnosis of the type of osteomyelitis or the exclusion of other bone disorders. Although there were always an increased number of plasma cells in the specimens from our patients, there were frequently transitional appearances varying from sclerosing osteomyelitis to Brodie's abscess. For this reason, we suggest that the term "primary chronic osteomyelitis" should be used. This makes it possible to distinguish the condition from acute and secondary osteomyelitis as well as from other diseases, such as bone tumours. All our patients were treated by local resection of the osteomyelitis lesion and they all recovered uneventfully; there were no local recurrences.