Combined therapy with the proton pump inhibitor omeprazole and amoxicillin has become an important alternative in the treatment of ulcer disease associated with Helicobacter pylori infection. Due to the high efficacy in eradicating H.pylori, missing resistance of H.pylori against amoxicillin and high tolerability and digestibility this regimen may be recommended for widespread routine use. In a randomized, double-blind multicenter trial an H.pylori eradication rate of over 90% has been achieved for the first time by dual therapy using a daily omeprazole dose of 120 mg (3x40 mg) in combination with 3 x 750 mg amoxicillin for 14 days, which is comparable with classical triple therapy containing bismuth and two antibiotics. On the basis of an "intention-to-treat-analysis" dual therapy of omeprazole 3x40 mg + 3x750 mg amoxicillin is considered at present to be the most effective regimen for the treatment of H.pylori-associated diseases.