Inducible nitric oxide synthase (iNOS) are important inflammation enzyme and severe up-nitric oxide (NO) production by this enzyme has been intricate with pathogenesis of atopy dermatitis. The present study was designed in order to determine whether Cheonggi-san could inhibit atopy dermatitis through modulation of iNOS mRNA expression and NO production. We found that iNOS mRNA expression and NO production in RAW 264.7 macrophages stimulated with lipopolysaccharide dose-dependantly decreased by Cheonggi-san extract treatment (0.5 - 2.0 mg/ml). The distribution of iNOS positive reacted cell in NC/Nga mice with atopy dermatitis were decreased by Cheonggi-san extract treatment (2.5 ml/kg/day) and apoptosis were increased. These data likely indicate that Cheonggi-san may act as inflammatory regulator for atopy dermatitis and may be possible to develop useful agent for chemoprevention of NO intricate inflammatory diseases.