Measurable amounts of viable and functional polymorphonuclear neutrophils (PMNs) are recovered from pooled washings of the gingival crevice of healthy individuals. In the present study, we have assessed the ability of the PMNs removed from single healthy or diseased pocket sites to mount an oxidative burst when challenged with phorbol myristate acetate (PMA) and compared these activities with each other and with those obtained with autologous peripheral-blood PMNs. The oxidative burst after PMA stimulation was evaluated by using methods developed for the flow cytometer. The results showed that the PMNs collected from untreated disease sites were minimally responsive to PMA when compared with peripheral-blood PMNs collected at the same time from the same individual. Thus, whereas the peripheral-blood PMNs exhibited significantly lower resting oxidative product formation and a 500% increase when stimulated with PMA, all gingival-crevicular PMNs exhibited significantly higher resting formation of oxidized products but only a 150% increase after PMA stimulation. PMNs obtained from a consistently healthy site had significantly higher resting production of oxidized products and were able to mount the greatest absolute increase in oxidized products after PMA stimulation when compared with PMNs collected from diseases sites. Mechanical debridement of these diseased sites, which both reduced the bacterial numbers and restored clinical health, resulted in the recovery of gingival-crevicular PMNs that exhibited an oxidative burst more typical of that observed in PMNs obtained from healthy gingival sites and from the peripheral blood. This suggested that the PMNs collected from the diseased sites either had been exhausted by the large numbers of bacteria present in these sites or had been specifically inhibited by these bacteria.