This research was undertaken to find the in vitro. inflammatory action of 5,7-dimethyloxy-4-p.-methoxylphenylcoumarin and 5,7-dimethoxy-4-phenylcoumarin produced by Streptomyces aureofaciens. CMUAc130. We investigated the effects of 5,7-dimethyloxy-4-p.-methoxylphenylcoumarin and 5,7-dimethoxy-4-phenylcoumarin not only on the formation of NO, prostaglandin E₂ (PGE₂), and tumor necrosis factor-α. (TNF-α.) but also on inducible nitric oxide synthase and cyclooxygenase-2 (COX-2) in lipopolysaccharide (LPS)-induced murine macrophage RAW 264.7 cells. The data obtained were consistent with the modulation of iNOS enzyme expression. A similar fashion was also observed when LPS-induced PGE₂ release and COX-2 expression were tested. The significant inhibitory effects were shown in concentration-dependent manners. In addition, 5,7-dimethyloxy-4-p.-methoxylphenylcoumarin and 5,7-dimethoxy-4-phenylcoumarin also mildly but significantly reduced the formation of TNF-α.. These findings support the application of 5,7-dimethyloxy-4-p.-methoxylphenylcoumarin and 5,7-dimethoxy-4-phenylcoumarin as anti-inflammatory agents.