To clarify the changes in plasma proteinase inhibitors in renal diseases, we measured the activity of plasma α_1-antichymotrypsin(α_1-Achy) under sueh conditions. The level of plasma α_1-Achy activity was found to be significantly lower in idiopathic nephrotic syndrome (INS) at relapse than in INS during remission, as well as in patients with chance proteinuria and/or hematuria (CPH) and in normal control subjects. The α_1-Achy activity in CPH was signiificantly elevated compared with that in INS (p
