Chemiluminescence (CL) was examined in phytohemagglutinin (PHA)-stimulated control and lupus lymphocytes because oxidative radicals have the chemical potential to generate DNA changes recently observed in lupus lymphocytes. Increased CL was found in 30 of 65 PHA-stimulated lupus lymphocyte samples by a luminol assay. CL did not correspond statistically to oxidative potential measured by a nitroblue tetrazolium assay. CL did not appear to be related to disease activity, organ involvement, or drug therapy. However, six of six males tested had positive CL activity. Cocultivation of CL-positive PHA-stimulated lupus lymphocytes with metabolic inhibitors of various oxidative enzymes revealed that 50 microM arachidonic acid dramatically inhibited the excess oxidation. A specific inhibitor of 5-lipoxygenase activity, 3 microM nordihydroguaiaretic acid, abolished excess CL activity. These studies suggest that chemiluminescence assays can be used to better understand the oxidative metabolism in lupus lymphocytes. The enzyme 5-lipoxygenase may be dysfunctional in a subgroup of lupus patients.