The anti-inflammatory activities of five flavonoids, namely 5,7-dimethoxyflavanone (1), 5,7-dimethoxy-3',4'-methylenedioxyflavanone (2), isobonducellin (3), 2'-hydroxy-2,3,4',6'-tetramethoxychalcone (4) and bonducellin (5), all of them isolated from Caesalpinia pulcherrima L. was studied in lipopolysaccharide (LPS) and interferon (IFN)-gamma activated murine peritoneal macrophages. These five compounds significantly and dose-dependently inhibited the inflammatory mediators; nitric oxide (NO), and cytokines [tumor necrosis factor (TNF)-alpha and interleukin (IL)-12]. According to their inhibitory results, the order of anti-inflammatory potency was compounds 3>5>4>2>1. Furthermore, peritoneal macrophages were pre-activated with LPS/IFN-gamma for 24h, and determined the inhibitory effects of the above-mentioned isolates on the production of NO after a further 24h. The present study supports the use of Caesalpinia pulcherrima for the treatment of inflammatory diseases in traditional medicine. This is the first study on compounds 1-5 about their anti-inflammatory activities.