Tetrahydroisoquinolin-1-one derivatives having an amide group at position-4 orapharmaceutically acceptable salt thereof have an excellent antagonisticactivity on a bombesin-2(BB2) receptor. These compounds are also highly effective on stoolabnormality. Therefore, thesetetrahydroisoquinolin-1-one derivatives are useful as therapeutic agents fordiseases associated with aBB2 receptor, particularly IBS.