The identification of circulating autoantibodies against the M-type phospholipase A₂ receptor (anti-PLA₂R) in patients with idiopathic membranous nephropathy (iMN) has been a major discovery. Anti-PLA₂R can be measured by a commercially available test. It is suggested that measurement of anti-PLA₂R will change the diagnostic strategy in patients with nephrotic syndrome and may guide treatment in patients with iMN. We review the available evidence and caution against the immediate injudicious use of the assay in routine clinical practice.