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. 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, a thought-provoking sum by any economic metric.