The methanolic extract from the seeds of Psoralea corylifolia was found to inhibit production of nitric oxide (NO) in lipopolysaccharide-activated mouse peritoneal macrophages. Among the isolated compounds, bavachinin (IC 50 ‫62؍‬ m mM), isobavachalcone (17 m mM), neobavaisoflavone (ca. 29 m mM), corylifol A (ca. 21 m mM), and psoralidin (ca. 23 m mM) significantly inhibited the accumulation of nitrite (NO 2 ؊ ) as a marker of production of NO. Bakuchiol, which is mainly contained in the extract, also showed weak activity at 10 m mM, but cytotoxic effects were observed more than 30 m mM.