Clinical data of 65 patients with myeloma were analyzed to identify factors associated with hypoalbuminemia. The serum albumin level was not affected by patient age and gender, type of myeloma, and the occurrence of Bence Jones protein, lytic bone lesions, or hypercalcemia, and it was not related to changes in body weight or in liver and renal function. The albumin level, lower in patients with proteinuria, was unrelated to severity of proteinuria. Albumin level correlated significantly with the monoclonal IgG levels, hemoglobin concentration, clinical stage of disease, and estimated body tumor burden. Further analysis indicated the disease stage or the tumor burden as the dominant factor in determining albumin level. An albumin level of 29.0 g/L or less identified unequivocally advanced disease. Practically all patients with stage III myeloma had a serum albumin level of 37.0 g/L or less. Thus, hypoalbuminemia is primarily related to the extent of myeloma proliferation and is therefore of diagnostic and prognostic importance.