Cells from the human adenoid cystic carcinoma (ACC) line, KOA-1, originating from the minor salivary gland and showing histological features of a dominantly solid pattern of ACC, were transplanted into the subcutaneous tissue of nude mice. The occurrence of lung metastasis was then examined both histologically and by PCR with a human-specific base arrangement of the beta-globin gene. Histologic examinations revealed lung metastasis in 5 of 30 mice. On the other hand, PCR showed a higher positive rate: 26 of 67 mice (0/10 at 1 month, 5/15 at 2 months, and 21/42 at 3 months after the transplantation). When some lungs which showed positive results by PCR analysis were transplanted into other mice, KOA-1 tumors developed. The results suggested that this experimental model could be a standard in vivo model of metastasis of human ACC.