Taurine chloramine (Tau-Cl) was recently demonstrated to inhibit production of nitric oxide and tumor necrosis factor-alpha (TNF-alpha) by activated macrophages. Since increased production of prostaglandin E2 (PGE2), a reaction catalyzed by induction of cyclooxygenase-2 (COX-2), is also associated with the inflammatory response, we determined the effects of Tau-Cl on PGE2 production and on expression of COX-2 protein and COX-2 mRNA in activated RAW 264.7 cells, a murine macrophage-like cell line. Tau-Cl inhibited production of PGE2 in a concentration dependent manner with an IC50 of 0.4 mM. The decrease in PGE2 production was largely accounted for by decreased expression of COX-2 protein. Although the kinetics of COX-2 mRNA expression was altered in Tau-Cl treated cells, mRNA expression appeared to be quantitatively unimpaired. These results suggest that Tau-Cl affects the post-transcriptional regulation of COX-2 expression and support the idea that Tau-Cl may function as an inhibitory modulator of the inflammatory response.