In an uncontrolled trial, patients with IgA nephropathy (IgAN) were treated with drugs that can alter the intestinal mucosal permeability to food antigens. These drugs are known to ameliorate urinary abnormalities and histological lesions of IgAN associated with ulcerative colitis or Crohn’s disease [5-aminosalicylic acid (5-ASA)] or to prevent, in mice, the induction of IgAN-like disease by oral immunization [disodium cromoglycate (SCG)]. Nine patients [serum creatinine (s-Cr) less than 2 mg/dl; 24-hour proteinuria higher than 1.5 g, but not nephrotic) were treated with 5-ASA (2.4 g/day for 6 months); 9 similar patients were treated with SCG (400 mg/day for 6 months); the follow-up extended to 6 months after stopping therapy. The 5-ASA group showed a slight but not significant decrease in s-Cr, 24-hour/proteinuria, IgA circulating immune complexes (IgA-CIC) and IgA rheumatoid factor (IgA-RF); serum β2-microglobulin and serum IgA were unchanged; 2 of 9 treated patients showed, after 6 months of therapy, a reduction in proteinuria of more than 50% that lasted for the subsequent 18 months. The SCG-treated group showed a slight but not significant increase in 24-hour proteinuria and a significant decrease in serum IgA; unchanged were s-Cr, IgA-CIC, IgA-RF, serum β2-microglobulin; no patient treated with SCG showed a reduction in proteinuria of more than 50%. At the dosages and for the periods used, 5-ASA and SCG did not show a significant influence on clinical and laboratory parameters of disease in IgAN; other trials with increased dosages are warranted to definitely ascertain the possible therapeutic role of these drugs in I