Matrix metalloproteinase-3 (MMP-3) degrades extracellular matrix and may lead to development of dilatative pathology of ascending thoracic aorta. Expression of MMP-3 depends upon the 5A/6A polymorphism in the promoter region. An increased number of 5A alleles leads to high expression of MMP-3. Thus, objective of the study was to determine whether the 5A/6A polymorphism in the promoter region of MMP-3 gene is associated with the development of dilatative pathology of ascending thoracic aorta. We studied 76 patients (age ranged from 31 to 81 years; median age, 64 years) who underwent aortic reconstruction surgery due to dilatative pathology of ascending thoracic aorta and a random sample of the population (n=604) aged 25-64 years, all from Lithuania. DNA was analyzed by using real-time polymerase chain reaction to genotype polymorphism 5A/6A at a position -1171 of the MMP3 gene promoter. The prevalence of MMP-3 genotypes was similar in the group of dilatative pathology of ascending thoracic aorta and random sample of population. The frequency of 5A allele did not differ significantly between both groups and was 0.506 and 0.514, respectively. Male carriers of 5A/5A genotype were significantly younger compared with those with the 6A/6A genotype. In conclusion, the frequency of MMP-3 promoter 5A/6A genotypes did not differ between the group of patients with dilatative pathology of ascending thoracic aorta and the random sample of population, but the males with dilatative pathology of ascending thoracic aorta and 5A/5A genotype required aortic reconstruction surgery at the younger age than the males carrying 6A/6A genotype in the MMP-3 promoter region.