Objective: To study the antimetastatic function of the nm23-h1 gene on the high pulmonary-metastatic adenoid cystic carcinoma cell line (ACC-M). Materials and Methods: Twenty BALB/C nude mice were randomly divided into 2 groups: one group was injected with 5 x 10⁶ nm23-h1 positively-transfected cells via a tail vein; the other group was injected with nontransfected cells as control. One week later 2 mice from each group were sacrificed for gross and histological examination, and 4 weeks later the remaining mice. Results: There was no obvious difference between the 2 groups after 1 week. After 4 weeks there were many gray-white metastatic nodules on the surface of the lungs in the nontransfected group; in the transfected group there was just a slight increase. Histological study endorsed the gross observation. Conclusion: That nm23-h1 may inhibit the pulmonary metastasis of ACC-M.