Background: The existence of immunoglobulin light chain restriction (LCR) strongly indicates B cell monoclonality. Although LCR-deficient B cell malignancies are often observed, their details are barely known. Methods: We retrospectively analyzed LCR-negative diffuse large B cell lymphoma (DLBCL) to elucidate their clinical features. Consecutive DLBCL patients (n = 119), whose histological diagnostic specimens were analyzed by flow cytometry (FCM), were divided into 2 groups: LCR-positive and LCR-negative DLBCL. Cases wherein FCM did not capture tumor cells were excluded. Results: There were 91 LCR-positive (76%) and 28 LCR-negative (24%) DLBCL. The 2 groups did not differ with regard to background, including the International Prognostic Index (IPI), each factor of IPI, gender, bulky mass and B-symptoms. FCM analysis showed that CD10-positive cases were less frequent in the LCR-negative DLBCL group than in the LCR-positive DLBCL group. CD5-positive cases were absent in the LCR-negative DLBCL group. Chromosomal analysis showed that the frequency of BCL2, BCL6 and MYC translocations did not differ between the groups. There was no survival difference in the groups. Conclusion: LCR-negative DLBCL accounts for about one fourth of all DLBCL and their prognosis is similar to that of LCR-positive DLBCL. CD10-negative status might characterize LCR-negative DLBCL.