beta2-microglobulin is a non glycosylated single chain protein present in light chain of HLA-class I. It is synthesized in the body and excreted in the urine. Its level increases in the blood of the chronic renal failure patients and may deposit in the soft tissue as beta2-microglobulin derived amyloidosis, which appear clinically after 5 years of dialysis. We studied 64 patients (49(76%) men) with end stage renal disease (ESRD) on regular hemodialysis. The mean age was 34.3 +/- 12 years and the duration of dialysis ranged between 0.4-12 years. Twenty-five healthy persons with mean age 34 +/- 17.6 years were used as a control group. The blood level of beta2-M in the control group ranged from 0.73-3.81 mg/l, while the range in the study group was 5.2-51.8 mg/l. In the urine of the control group, beta2-M level ranged from 0-0.7 mg/l, while in the control group it ranged from 0.07-11.8 mg/l. There was significant difference in the beta2-M level in both control and study groups. A direct correlation was found between the duration of dialysis and the level of beta2-M in the blood. The traditional low flux dialyzer membrane had no effects on beta2-M level in our series. We conclude that there is increased tendency with time for retention of beta2-M in the ESRD patients on chronic dialysis. Using dialyzers with high flux synthetic membrane (e.g. acrylonitrile, polyamide, and polysulphone) rather than the low flux membrane may allow substantial removal of beta2-M molecules, especially in patients who have little chance of receiving renal transplantation.