 Clopidogrel causes significantly less peptic ulcer disease PUD and ulcer bleeding than low-dose aspirin in general population. However, clopidogrel is not safe enough for gastrointestinal GI mucosa in patients who had past history of aspirin-associated ulcer or ulcer bleeding. Aspirin plus proton pump inhibitor PPI is superior to clopidogrel alone in preventing recurrent ulcer bleeding in these high risk patients. 