Patients (15) with chronic renal failure had depressed neutrophil chemotactic responsiveness following several hemodialysis treatments. The chemotactic index (C.I.) of these patients was 12.7 .+-. 6.4 as compared with 72.8 .+-. 22.7 for controls (P < 0.001). Patients with chronic renal failure, not on hemodialysis, had only mildly depressed neutrophil chemotactic responsiveness (42.3 .+-. 15; P < 0.01). Thus, hemodialysis impairs neutrophil function and may contribute to the increased risk of infection in uremic patients. Chemotactic responsiveness returned to normal in 3 patients following renal transplantation.