Despite a general recognition that treatment of end-stage renal disease (ESRD) has become a large-scale undertaking, the size of the treated population and the associated costs are not well quantified. This report combines data available from a variety of sources and places the current (midyear 2001) estimated global maintenance dialysis population at just over 1.1 million patients. The size of this population has been expanding at a rate of 7% per year. Total therapy cost per patient per year in the United States is approximately 66,000 dollars. Assuming that this figure is a reasonable global average, the annual worldwide cost of maintenance ESRD therapy in the year 2001, excluding renal transplantation, will be between 70 and 75 billion US dollars. If current trends in ESRD prevalence continue, as seems probable, the ESRD population will exceed 2 million patients by the year 2010. The care of this group represents a major societal commitment: the aggregate cost of treating ESRD during the coming decade will exceed 1 trillion dollars, a thought-provoking sum by any economic metric.