Cardiac myxoma, a relatively common condition in adults, is exceptionally rare in childhood. It is usually observed in the left atrium. The condition may be latent and a chance echocardiographic finding or present with arrhythmias, intermittent mitral obstruction or embolic phenomena. The authors report the case of an 11-year old child with no previous medical history, admitted to hospital after sudden right hemiplegia due to an ischaemic cerebrovascular accident. The investigation of a cardiac embolic abnormality led to the finding of a very large left ventricular tumour inserted into the mitral annulus and prolapsing into the left ventricular outflow tract, the histological examination of which confirmed the diagnosis of myxoma. Cardiac myxomas in children seem to have a much more variable site of implantation than in adults, especially in the right heart in infancy. Treatment is always surgical. Echocardiography should be requested early in children presenting with a murmur of recent origin, malaises, or unexplained inflammatory syndromes, and would seem to be the only means of avoiding the severe embolic complications of these histologically benign tumours.