Objective: To determine the characteristics of oligoclonal bands that are frequently detected by serum protein electrophoresis (SPEP) and immunofixation electrophoresis (IFE) after stem cell transplantation. Methods: We retrospectively analyzed 56 patients with multiple myeloma (MM) undergoing transplantation, and standard immunofixation electrophoresis was used to identify and quantify paraproteins. Results: The median follow-up was 35 months (range, 10-76months) and 21 patients relapsed. Twelve (25.0%) demonstrated oligoclonal bands after a median time 1.4 months (range, 1-3months), with a median duration of 5.8 months (range, 1-15months). The majority patients with oligoclonal bands had normal quantities of immunoglobulins and the one year event free survival (EFS) was 92%, even higher than for patients without OBs (P=0.002). Conclusion: Oligoclonal bands frequent develop post-transplantation in MM cases. In the vast majority of patients, they may not represent relapsed disease, and more likely represent a transient phenomenon representing recovery of impaired immunoglobulin production.