Background. Plasma levels of some pro-inflammatory cytokines and soluble adhesion molecules have been suggested to be useful parameters to assess the activity of antineutrophil cytoplasmic antibody (ANCA)-positive vasculitis and lupus nephritis. We hypothesized that the renal activity of these diseases is better reflected by the urinary excretion and fractional excretion of these molecules. Methods. Plasma levels and urinary excretion of tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, IL-8, and the soluble cell adhesion molecules sICAM-1 and sVCAM-1 were measured by enzyme-linked immunosorbent assay (ELISA) in 14 patients with ANCA-positive renal vasculitis (eight active, ANCA-A; six in remission, ANCA-R), six patients with active lupus nephritis (LN), 15 patients with IgA nephropathy (IgAN) and nine healthy subjects. Fractional excretion of selected cytokines and adhesion molecules was also calculated. Results. Patients with ANCA-A had increased urinary excretion and fractional excretion of TNF-alpha (9.27+/-3.19% vs 0.58+/-0.02%, P<0.01), IL-6 (120.79+/-65.83% vs 1.89+0.34%, P<0.01) and increased fractional excretion of IL-X (23.34+/-6.38% vs 2.56+/-1.07%, P<0.01) and sVCAM-1 (0.81+/-0.33% vs 0.03+/-0.02%, P<0.01) compared with controls. Urinary excretion of TNF-alpha and IL-6 and fractional excretion of TNF alpha, IL-G and IL-8 were higher in ANCA-A than in ANCA-R. Patients with LN had increased plasma TNF-alpha (20.52+/-2.01 pg/ml vs 12.33+/-0.23 pg/ml, P<0.05) and sVCAM-1 (1537.88+/-276.36 ng/ml vs 692.26+/-44.42 ng/ml, P<0.05) and increased urinary excretion of TNF-alpha (2.81+/-0.51 mu g/mol creat vs 0.98 +/- 0.05 mu g/mol creat, P < 0.01), IL-S (35.78+/-14.03 mu g/mol creel vs 12.46+/-5.19 mu g/mol creat, P<0.05) and sVCAM-1 (48.98+/-20.20 mu g/mol creat vs 2.92+/-1.35 mu g/mol creat, P<0.01) compared with controls. Patients with IgAN had, in comparison with controls only increased plasma TNF-alpha (18.10+/-0.57 pg/ml vs 12.33+/-0.23 pg/ml, P<0.05). Conclusions. Urinary excretion and fractional excretion. but not plasma levels, of selected proinflammatory cytokines (TNF-alpha, IL-6 and IL-8) were increased in patients with active ANCA-posirive renal vasculitis, but not in ANCA positive vasculitis in remission. These parameters may be useful to monitor the activity of this disease