Objectives: The aim of this study was to determine the effects of Salvia miltiorrhiza (SM) extract in urethane-induced lung tumorigenesis in A/J mice. Methods : We examined change of body weight, histological, apoptosis, immunohistochemical and gene expression of cyclooxygenase (COX-2) in lung tumors. Mice were divided into 3 groups: normal, saline, and experimental group administered SM extract after injection with urethane. Results : Histological observation showed shrunken alveoli in the control group, but recovered from damage in the SM extract administered group. The COX-2 positive materials were observed in the smooth muscle of terminal bronchiole and alveoli from the control group, but these positive materials decreased in the SM extract treatment group. The results of electron microscopical observation, dilated capillary and degenerated endothelia were observed in the control group. The apoptotic nuclei increased more in the control group compared with the normal and SM extract administered groups. Serial sections of the whole lung showed solid and papillary tumors. The size and number of tumors decreased in the SM groups compared with the control groups. Conclusions : These results suggest the possibility that SM may exert an anti-tumor effect on urethane-induced lung tumorigenesis.