We analyzed the evolution with age of the frequencies of the I/D polymorphism of the angiotensin I-converting enzyme (ACE), a1166c of the angiotensin II AT1 receptor (AT1R), M235T of the angiotensinogen (AGT) and A225V of their methylenetetrahydrofolate reductase (MTHFR) gene in a healthy (H) population and the subsequent comparison to age- and sex-matched groups of myocardial infarction (MI) subjects. A total of 472 H subjects were divided into three groups < 30, 30-55 and > 55 years old and 277 individuals with MI into two groups 30-55 and > 55 years old. The evolution with age showed that the AGT M allele (P < 0.001) and the MTHFR V allele (P < 0.05) frequency decreased with age in H men. The comparison between healthy and MI groups showed that the MM genotype frequency increased in MI men > 55 years (OR =4.16; 95% CI; 1.72-10.1) The cc genotype showed a similar behaviour (OR = 3.96; 95% CI; 1.21-12.9). In men, all the combinations with MM genotype presented a high risk, with OR values between 1.10 and 7.22. In women, the cc genotype increased in the MI > 55 group (OR = 6.66; 95% CI; 2.02-21.9). All the combinations with the cc genotype showed OR values between 1.71 and 13.3. The MM genotype in men and cc genotype in men and women, are independent risk factors for MI. We propose that the study of the allele frequency evolution in an H population at different ages is essential to determine risk factors for MI in case-control studies, since data from isolated age-matched groups can be misinterpreted.