Long-term follow-up evaluation of biofiltration treatment in 7 patients is presented. These patients experienced frequent episodes of hypotension during acetate hemodialysis. A 3-year biofiltration treatment reduced by 43% episodes of symptomatic hypotension and produced a significant increase in the pretreatment pH and plasma bicarbonate levels. The beta 2-microglobulin level was significantly reduced during biofiltration therapy. The mean systolic and diastolic blood pressures slightly increased during biofiltration. Uremic polyneuropathy, as demonstrated by an increase in motor nerve conduction velocity, slightly improved. The patients reported increased comfort during biofiltration therapy.