A case of right atrial myxoma presenting with right heart failure and proteinuria is described. Proteinuria was variable and this corresponded with the degree of systemic venous congestion. On one occasion the proteinuria was within the nephrotic range. There was no evidence of intrinsic renal pathology. The right heart failure and proteinuria resolved after tumour removal, suggesting that the etiology of urinary protein loss was a reversible increase in glomerular permeability.