Rat alveolar macrophages, labeled with 3H-arachidonic acid, were treated with t-butyl hydroperoxide (tBOOH). Treatment of cells with 100 microM tBOOH led to a rapid increase in 12-hydroxyheptadecatrienoic acid (12-HHT) within 2.5 minutes. At 15 minutes, 12-HHT levels appeared to plateau as there was no further increase at 30 minutes. TxB2 levels increased in a similar manner to that found with 12-HHT; however, only the level at 15 minutes was statistically increased. TxB2 levels also appeared to plateau at 15 minutes. Indomethacin, at a concentration of 1 microM, significantly inhibited TxB2 and 12-HHT production by approximately 90%. Desferal, an iron chelator, had no effect on alterations of biosynthesis of cyclooxygenase products by macrophages treated with tBOOH. No evidence of lipoxygenase products was found. Thus, these results suggest that tBOOH rapidly and selectively stimulated arachidonic acid metabolism through the cyclooxygenase pathway in rat alveolar macrophages. The stimulation of cyclooxygenase activity was transient with a maximum rate observed at 100 microM tBOOH.