Sixteen patients with solitary plasmacytomas of bone (SPB) have been reviewed with regard to prognosis, response to treatment, and protein findings.Three patients developed multiple myeloma (MM), and 2 of the patients died due to dissemination. Local recurrence was not seen. Moreover, this study confirms other reports as for the good prognosis of SPB.Intracytoplasmatic immunoglobulin (Ig) has been characterized in tumour tissue from 10 cases by the peroxidase‐anti‐peroxidase (PAP) method. The tumour tissue stained positively with monoclonal Ig in 8 out of 10 cases. The distribution of myeloma proteins did not differ from that reported in MM.Furthermore, there was complete concordance between immunoglobulin class of paraprotein and intracytoplasmatic