The gene for methylenetetrahydrofolate reductase (MTHFR) has two different alleles (C and T), where the T is associated with decreased enzyme activity, hyperhomocysteinaemia, and increased risk for thromboembolism in coronary heart disease (CHD). The study was conducted using a sample of 378 Hungarian newborn infants: 96 control subjects (age: 59.9+/-8.6 years) with chest pain and 315 CHD patients (61.4+/-7.5 years). All adult subjects had undergone coronary angiography. It can be concluded that the carriers of T allele with CHD died earlier due to myocardial infarction and the C allele with lower homocysteine level may provide protection against fatal coronary artery occlusion.