Dialyzed neutrophils were isolated at time 0, 5, 15 and 60 min after the onset of hemodialysis in patients successively treated on 5 new and reused membranes, that is cuprophan (CU), cellulose acetate (CA), polysulfone (PS), polycarbonate (PC) and polyacrilonitrile (PAN). Production of oxygen radicals was monitored by luminol and lucigenin-enhanced chemiluminescence (CL). During dialysis with CU and PC, cells remaining in circulation at the maximum neutropenia showed a significant decrease of luminol-enhanced CL, whether stimulated with opsonized zymosan or phorbol myristate acetate. This defect was transient and the responses normalized at 60 min or upon reuse of the membranes. Among the other membranes tested, only cells collected during the first use of PS showed an impaired CL response to phorbol myristate acetate, but not to opsonized zymosan. CL again normalized upon reuse. At 5 min of dialysis with each membrane, a plasma factor appeared that was able to stimulate oxygen radical production by autologous dialyzed and control cells. A dissociation between the oxidative responses of dialyzed neutrophils and neutropenia was observed depending on the nature of the membranes, suggesting that neutropenia is a multifactorial process in which oxygen radical production appears as an early disturbance.