Previous studies from our laboratory have shown that condensed tannin isolated from cotton bracts is a potent agonist for the release of arachidonic acid (AA) from membrane phospholipids of rabbit alveolar macrophages. Activation of AA release by most agonists appears to require the transport of sodium from the cell exterior into the cytoplasm. When rabbit alveolar macrophages were incubated in medium containing sodium but no potassium ions, zymosan and tannin both induced the release of expected levels of AA. When the macrophages were incubated in medium containing potassium but no sodium ions, zymosan-induced AA release was significantly inhibited as expected. However, in this same medium tannin induced a level of AA release equal to or greater than that observed in the sodium ion medium. These results demonstrate that tannin-mediated release of AA does not require sodium transport.