The biochemical mechanisms for the termination of the respiratory burst are likely to be multifactorial. Alterations in the endogenous oxidant-scavenging mechanisms can modulate the kinetics of the termination phase of neutrophil superoxide production. These are most apparent when those alterations are found in the neutrophils of certain patients. The use of inhibitors of the oxidant scavenging systems in normal neutrophils has not yielded results that exactly mimic the studies with neutrophils from the patients. For example, the glutathione reductase-inhibited neutrophils (from the action of BCNU) do not show the same degree of abnormality as do the neutrophils from the patient with glutathione reductase deficiency. Further investigations on the mechanisms of inactivation of the NADPH oxidase are warranted in order to gain a greater understanding of this important regulating mechanism.