The authors report the case of a 65 year old man who presented with an acute coronary syndrome without ST elevation due to acute stent thrombosis 12 hours after implantation. Recent reports in the literature suggest the role of resistance to antiplatelet drugs in acute, subacute or late stent thrombosis. This patient was included in a protocol studying the response to antiplatelet drugs in patients undergoing coronary stenting and fulfilled the criteria of resistance to clopidogrel. This clinical case illustrates the possible role of "resistance" to antiplatelet drugs in stent thromboses.