Wilms's tumours that extend by direct intravascular spread into the right side of the heart are rare. A case of such a tumour was diagnosed by ultrasound. A one stage resection was performed on cardiopulmonary bypass and with profound hypothermic circulatory arrest. It was followed by adjunctive chemotherapy and radiotherapy. The child was alive and tumour free 18 months later. A review of 17 other similar cases indicated that multimodal treatment is justified in patients with extensive intravascular spread of Wilms's tumours.