Objective: CD20 expression was reported at different rates in patients with multiple myeloma. The importance of this B-cell antigen for plasma cells is still unknown. This study aimed to investigate CD20 expression of myeloma cells in bone marrow, and any relationship between the stage of disease, isotype and clinical features. Methods: Sixty-one patients who were admitted to the hematology clinic of the Adnan Menderes Medical School with the diagnosis of multiple myeloma according to the criteria of the "International Myeloma Working Group" were enrolled in this study. Age, gender, Durie-Salmon stage, history of autologous hematopoietic stem cell transplantation, and the distribution pattern and positivity of CD20 expression on multiple myeloma cells in bone marrow were evaluated. The Mann-Whitney U and chi-square tests were used for statistical analysis with a p-value < 0.05 being accepted as statistically significant. Results: Thirty patients (48.9%) had positive scores for CD20 with the distribution pattern being most likely interstitial in 55.6% of the cases. There was no statistically significant difference between immunohistochemical positivity for CD20 expression on multiple myeloma cells, immunoglobulin type, and the stage of disease. Conclusion: The combination of immunohistochemical studies with flow cytometry may reveal the importance of CD20 positivity in patients with multiple myeloma more clearly.