Objective To study the relationship between the apolipoprotein B(apo B) gene polymorphism and mycoardial infarction.Methods Two polymorphic sites of the apo B gene,Xba1 and Msp1 were examined by PCR in a sample of 65 patients with myocardial infarction(MI) and 60 healthy individuals selected from a population of the chinese Han nationality.Results The frequency of X+allele(presence of Xba1 cutting site)in MI cases was significantly higher than that in controls(P