Artemisia princeps Pampanini (family Asteraceae) is an herbal medicine widely used as a hepatoprotective, antioxidative, anti-inflammatory, and antibacterial agent in Korea, China, and Japan. This study aimed to elucidate the anti-inflammatory effect of the main constituents, eupatilin and jaceosidin, isolated from Artemisia princeps. We used carrageenan-induced inflammation in an air pouch on the back of mice and carrageenan-induced hind paw edema in rats to determine the anti-inflammatory effects of eupatilin and jaceosidin. Inflammatory makers, such as expression of pro-inflammatory cytokines and cyclooxygenase (COX)-2, and activation of nuclear factor-kappa B (NF-kappaB), were measured by enzyme-linked immunosorbent assays and immunoblot analyses. Eupatilin and jaceosidin blocked carrageenan-induced increase in leukocyte number and protein levels in air pouch exudates. Eupatilin and jaceosidin inhibited COX-2 expression and NF-kappaB activation, and markedly reduced TNF-alpha, IL-1beta, and prostaglandin E2 (PGE(2)) levels. They also inhibited hind paw edema induced by carrageenan. Eupatilin and jaceosidin had similar activity. These findings suggest that eupatilin and jaceosidin may reduce inflammation by inhibiting NF-kappaB activation, and that Artemisia princeps inhibits inflammation because of these constituents.