Myxomas are uncommon primary cardiac tumours, usually affecting the left atrium. We describe an unusual presentation of cardiac myxoma with asymptomatic proteinuria and haematuria. Surgical excision of the tumour resulted in complete resolution of the urinary abnormalities. The production of antiendothelial cell antibodies and interleukin-6 by cardiac myxomas may be relevant as these substances have been implicated with the development of renal injury and proteinuria.