The inhibitory effects of components derived from Cinnamomum cassia leaf on nitric oxide (NO) production in RAW 264.7 cells and on expression of inducible NO synthase (iNOS) were determined and compared to those of three commercially available components. Spectral analysis characterized the active constituent of this C. cassia extract as cinnamyl alcohol. The inhibitory effects varied with both chemical and concentration used. Cinnamyl alcohol showed inhibitory effects on NO production of 62.5%, 41.8%, and 22.1% at 1.0, 0.5, and $0.1;{mu}g/{mu}L$, respectively. However, little or no inhibitory effect was observed for cedrene, cinnamic acid, copaene, eugenol, and limonene. Suppression effects of cinnamyl alcohol on iNOS expression were revealed by Western blot analysis. As a naturally occurring therapeutic agent, cinnamyl alcohol could be useful for developing new types of NO inhibitors.