Clopidogrel is a new drug in the recently developed class of thienopyridine derivatives that inhibits platelet function by an inhibitory action exerted through the membrane adenosine diphosphate receptor. Clopidogrel is a prodrug that must be metabolized to an active metabolite in the liver. The basic chemistry, pharmacodynamics and pharmacokinetics of the drug are reviewed. Clinical trials with clopidogrel, including its use in patients with stents postangioplasty, adverse reactions, and potential advantages over other agents are summarized.