A nationwide survey was made to find out patients with malignant tumours among the dialysis population. A total of 354 malignant tumours were detected during the time of survey. Consistent with the incidence in the Japanese general population, the most frequently detected malignant tumour was gastric cancer, accounting for about one third of the total. Overall the incidence of tumour death was 2.31 times higher in males and 4.3 times higher in females. However, the high incidence of gynaecological and urinary tract tumours would suggest that some of them might be causative factors for the development of renal failure.