Type B lactic acidosis is a rare complication of hematologic malignancies. The exact mechanism of this process is not well understood. Because caregivers may not be aware of the association of type B lactic acidosis with hematologic malignancies, it may go unrecognized as a cause of acidosis in these patients. We report the cases of 7 patients with type B lactic acidosis who were cared for by members of the Brown Medical School Hematology/Oncology Division. Of the 7 patients reported, 5 had lymphomas and 2 had chronic lymphocytic leukemia. One of the lymphomas was a T-cell lymphoma. Of the patients we were able to evaluate, there did not seem to be a unique cluster of differentiation marker in association with type B lactic acidosis. We also review 14 additional cases, most reported since 2001. From our review of the literature, we suggest that a deficiency of thiamine or riboflavin may play a more pivotal role than previously recognized in the development of type B lactic acidosis associated with malignancy. Further investigation should be undertaken to learn if thiamine or riboflavin replacement might be useful in treating this disorder.