Background: Acute myocardial infarction (AMI) is one of the most common reasons of hospitalization in western countries. The rate of early mortality (the first 30 days) caused by AMI is about 30%. Many studies have introduced the infection with Helicobacter pylori and mycoplasma pneumonia as causes of AMI. However, some other studies on the effect of mycoplasma pneumonia, Helicobacter pylori, and blood group on the incidence of heart attack showed contradictions that might be due to the ethnical and racial heterogeneities. Therefore, this study was conducted to determine the correlation of the infection with Helicobacter pylori and mycoplasma pneumonia and blood group with AMI in Qazvin Province, Iran. Objectives: In this respect, the infection with Helicobacter pylori and mycoplasma pneumonia can be taken as a risk factor for AMI thereafter if there is a strong correlation between infection with Helicobacter pylori and mycoplasma pneumonia and AMI, and also the high-risk blood groups can be identified, and consequently, risk factors for AMI be reduced through early treatment. Materials and Method: This case-control study was performed in teaching hospitals in Qazvin. After completing the sample size in both groups (blood serum of 90 patients with a history of infarction as the case group and blood serum of 90 other people that matched for age and sex with the first group and had no history of infarction as the control group), the studies were performed to determine the correlation of AMI with mycoplasma pneumonia through the level of IgG antibody, with Helicobacter pylori through the level of relevant antibodies (IgA and IgG), and with blood groups through back-type method. Results: Men and women of the case group comprised 63.3% and 36.7%, respectively, and men and women of the control group comprised 67.8% and 32.2%, respectively. The level of Helicobacter pylori IgG was considered negative in 1.1%, borderline in 5.6%, and positive in 93.3% in the case group and neg-* Corresponding author.