Monoclonal gammopathy of undetermined significance (MGUS) is defined by the presence of a serum M-protein at a concentration of 3 g/dL or less, with less than 10% plasma cells in the bone marrow, and the absence of lytic bone lesions, anemia, hypercalcemia, and renal insufficiency related to the plasma cell proliferative process. The annual risk of MGUS progressing to a symptomatic plasma cell proliferation or other related malignancy is approximately 1%. The association between malignancy and venous thromboembolism (VTE) is well recognized. In this retrospective study of MGUS patients, VTE was seen in 8% (9/112) of patients, a rate that is 22.8-fold higher than that in the general population (P is less than .001). Although many studies have identified VTE as a marker for subsequent malignancy, we did not find a significant difference in the incidence of VTE as a function of the risk factor group.