Atherothrombotic disease is the leading cause of death worldwide. Most casualties are due to acute myocardial infarction (AMI). Patients younger than 45 years account for 5-10% of AMI cases. These patients generally do not display typical atherothrombotic risk factors. Our cross-sectional study included adult patients under 45; men and women with AMI were included. A control group of healthy individuals matched for age, sex, and blood group was included to determine the role of several atherothrombotic risk factors on AMI. One hundred and sixty patients were included, the control group was comprised by 77 males (m) and 83 females (f) Our results indicate that 25% of patients (23 m and 18 f) had increased FVIII compared with 8.8% of control subjects. Mean FVIII activity for patients and controls was 134 mg/dl (95%CI=114) vs. 118 mg/dl (95%CI=128-140), respectively (p=0.001). Prevalence of elevated FVIII was higher than the one found for hypertension or diabetes mellitus. HDL cholesterol was higher among patients than controls. Quantitative variables associated with AMI were high FVIII activity, blood monocyte count and HDL cholesterol. Classical atherothrombotic risk factors do not fully explain AMI events in the young. High levels of FVIII activity is a moderate but common risk factor in young people suffering AMI.