Slightly increased urinary albumin excretion is frequently found in patients with lymphoma and other malignancies but the pathophysiological mechanisms have yet to be clarified. In this study, parameters of renal function in lymphoma patients with microalbuminuria were evaluated. Sixty-seven patients with histologically proven diffuse large B-cell lymphoma were included in the study at diagnosis. Urinary albumin excretion was measured by immunoturbidimetry and microalbuminuria was defined as an excretion rate between 20 and 200 microg/min. Glomerular function was further estimated by renal clearance of creatinine and IgG, and the IgG/IgG4 charge selectivity index. Tubular function was evaluated by renal clearance of beta(2)-microglobulin. The median value of IgG clearance was increased in the microalbuminuric patients (0.22 versus 0.18 microl/min; p = 0.03). The median selectivity index was significantly lower in patients with microalbuminuria (1.0 versus 2.2; p<0.0001). Urinary albumin excretion was correlated with both the renal clearance of IgG (p<0.0001) and the selectivity index (p<0.0001). These data suggest that a slightly elevated level of urinary albumin excretion in a population of patients with aggressive lymphoma reflects altered glomerular permselectivity probably due to a defect in charge selectivity. The glomerular sieving dysfunction may be associated with an inflammatory response to the malignancy. Further studies are needed to validate the clinical impact of the renal parameters in lymphoma patients.