In Japan, a phase 3 trial of 1-week triple therapy with lansoprazole(L), amoxicillin(A), and clarithromycin(C) was finished in March, 2000. Patients were randomized into three groups: L 30 mg bid and placebos, and L 30 mg bid, A 750 mg bid and C 200 mg bid or 400 mg bid. Eradication rates were high in group LAC200(88-91%) and group LAC400 (84-89%). Next, a phase 3 trial of 1-week triple therapy with omeplazole (O), A and C was finished in 2001. Eradication rates were 78.8% in the group of O 20 mg, A 750 mg and C 400 mg bid, and 83.0% in the group of O 20 mg, A 1,000 mg, and C 500 mg bid.