The morbidity and mortality of hemodialysis by internal central venous catheterization in the subclavian and internal jugular positions are reviewed. A follow-up study was performed in our unit over 10 years (786 catheterizations). The most frequent complications were inadequate flow (7.6%) inadvertent withdrawal (5.6%) and bacteremia (5.1%). The overall complication rate was 27.2%. Kinking (p less than 0.001), bleeding (p less than 0.01) and bacteremia (p less than 0.05) occurred more frequently in patients with chronic renal failure, compared to patients with acute renal failure. Inadvertent withdrawal was the only complication observed more frequently in the internal jugular than in the subclavian position (10.8 vs. 4.3%; p less than 0.01). Bacteremia occurred more frequently after prolonged periods of catheterization (greater than 10 days). No fatal complications were observed. To obtain a more accurate idea about mortality, two supplementary large groups were studied: a review of 11 published series (1,542 catheterizations) and a questionnaire-based survey of 16 dialysis centers (approximately 4,000 catheterizations). Six fatalities were registered: 1 due to septicemia (in the literature review) and 3 due to traumatic perforation of the cardiac or the vessel wall, 1 to septicemia and 1 to air embolism (in the questionnaire-based survey). Based on the three different groups studied, the mortality of catheter dialysis could be estimated to be between 0 and 1.25/1,000 catheterizations.