AbstractA therapeutic trial of plasma exchange was performed in 13 patients with documented progressive IgA nephropathy. Comparison of the rate of deterioration in renal function before, during, and after plasma exchange demonstrated significant improvement during plasma exchange. Seven patients had a slowed rate of deterioration by plasma exchange, but achieved a decrease in serum creatinine level. Favourable response was correlated with rapidity of deterioration preplasma exchange (Plt; 0.01) and was apparent within 4 weeks of commencing therapy in those patients who responded. There was no overall difference between the deterioration rates pre‐ and postplasma exchange. In patients in whom creatinine decreased on plasma exchange, the initiation of subsequent dialysis was delaye