Today, following coronary stenting, clopidogrel has largely replaced ticlopidine as part of combination antiplatelet therapy following coronary stenting primarily due to its better tolerability. While there is no randomized, blinded, efficacy trial of ticlopidine versus clopidogrel, there are ample data from a number of observational studies, randomized non-blinded trials, and a randomized blinded safety trial to prove that clopidogrel is not only safer than ticlopidine, but also at least as efficacious following stenting. With over 10,000 treated patients, pooled data suggest similar rates of stent thrombosis (clopidogrel 0.98% vs. ticlopidine 0.98%) and lower rates of major adverse cardiac events with clopidogrel (clopidogrel 1.63% vs. ticlopidine 4.52%, p<0.001), with a clear advantage for clopidogrel regarding adverse events (clopidogrel 5.91% vs. ticlopidine 9.75%, p<0.001). With clopidogrel's superior safety and at least equivalent efficacy, the question of "which thienopyridine?" post-stenting has been answered. Now the questions "how much?", "how soon?" and "how long?" must be addressed. The Clopidogrel for the Reduction of Events During Observation (CREDO) trial is a multi-center, double-blind, randomized trial designed to answer these remaining questions. CREDO will evaluate the efficacy and safety of clopidogrel pretreatment versus no pretreatment, and prolonged (1 year), versus short-term (1 month) dual antiplatelet therapy in 2,000 patients undergoing planned or highly probable coronary intervention with a stent.