Human alveolar macrophages, obtained during diagnostic bronchoscopy, were maintained in monolayer culture. Challenge of these cells (greater than 95% purity) with 1.2 mg/ml zymosan A particles (opsonized with human serum) was followed by a rapid release of leukotriene B4 into the medium, 7.28 +/- 5.99 ng/mg cell protein at 2 h (mean +/- S.D.4, n = 4). Leukotriene B4 was identified and measured by a novel technique employing capillary column gas chromatography coupled to negative ion chemical ionization mass spectrometry. The release of thromboxane B2, prostaglandins D2, E2, F2 alpha and the lysosomal enzyme N-acetyl-beta-D-glucosaminidase was also measured. Thromboxane B2 was the most abundant metabolite of arachidonic acid released into the culture medium (65.2 +/- 14.8 ng/mg cell protein 2 h after the addition of zymosan A, n = 4), and the synthesis of thromboxane B2 was inhibited by greater than 90% in 1 microM Na flurbiprofen. Inhibition of cyclooxygenase activity was accompanied by a 2-fold increase in leukotriene B4 synthesis.