Abstract We have compared assays for products of the neutrophil respiratory burst in normal EBV-transformed B cell lines stimulated with agonists of protein kinase C. Those measuring O 2 − directly or its immediate product, H 2O 2, were successful. Of these, the most sensitive were the lucigenin- and luminol-based chemiluminescence assays for O 2 − and H 2O 2 respectively. Cell lines from CGD patients, with X-linked or autosomal recessive genetic defects in the neutrophil NADPH oxidase, did not respond in these assays, indicative of their inability to produce O 2 −. The defects in the lines studied encompass both proteins forming the cytochrome b −245 membrane component, and the 47 kDa cytosolic component of the NADPH oxidase. The possession of the disease associated phenotype by these cell lines provides evidence that in the normal situation both neutrophils and B cells produce O 2 − via the same system.