ABSTRACT—Prostaglandin E2production by tissue‐fixed macrophages (MØ) after severe injury contributes to an enhanced susceptibility to infection and sepsis. The purpose of this study was to investigate the effect of cyclic adenosine monophosphate (cAMP) on prostaglandin (PGE2) production and cyclooxygenase II (COX‐2) gene activation in LPS‐stimulated macrophages (MØ). RAW264.7 cells, a mouse MØ cell line, were exposed to various concentrations of dibutyryl cAMP ± lipopolysaccharide (10 &mgr;g/mL) stimulation. Total MØ ribonucleic acid (RNA) was harvested for the determination of COX‐2 messenger RNA (mRNA) with mouse complementary deoxyribonucleic acid (cDNA) by Northern blot assay. MØ supernatant was collected for the measurement of tumor necrosis factor (TNF) by L929 bioassay and PGE2by enzyme‐linked immunosorbent assay (ELISA), respectively. MØ NF&kgr;B activity was determined by electrophoretic mobility shift assays (EMSA). Dibutyryl cAMP significantly inhibited TNF production by LPS‐stimulated MØ. Dibutyryl cAMP (1 mM) alone induced PGE2production. Dibutyryl cAMP (100 &mgr;M and 1 mM) also augmented PGE2production by LPS‐stimulated MØ. Dibutyryl cAMP had similar effect on MØ COX‐2 mRNA expression and NF&kgr;B activity. Our data demonstrate that cAMP modulates MØ TNF production and upregulates COX‐2 gene and PGE2production.