Identical twins presented at the same time with renal failure. They also recalled a simultaneous history of "nephritis" as early as the age of 6 years. Renal biopsies revealed variably thickened glomerular basement membranes with the lamellation and splitting characteristic of Alport's syndrome. Bilateral sensorineural deafness was demonstrated in both twins on audiometric testing. A positive family history in the mother and one elder sister confirmed the diagnosis of Alport's syndrome. This is the first reported case of Alport's syndrome occurring in monozygotic twins.