The combined products of antacid and anti-ulcer agent were prepared with antacid composed of aluminium hydroxide dried gel, magnesium hydroxide and simethicone with a ratio of 1:1:0.1 (M) and anti-ulcer agent, aceglutamide aluminium (AGA). The efficacy of antacid was evaluated in vitro with Fuchs, Johnson-Duncan and Rosset-Rice methods and in vivo using an aspiration method in rat. The addition of anti-ulcer agent did not affect the neutralizing capacity of M significantly. The combined products with the M/AGA ratios of 2.3:1 and 3.4:1 produced the maximum pH of $4.0{sim}5.8$ and the duration time of $64{sim}137$ min in vitro test. The in vivo neutralizing test in rats showed the rapid increase of gastric pH up to 3.5 within 30 min and the gastric pH of $4{sim}6$ was kept for 5 hr.