The intima-media complex thickness (IMT) was evaluated in 472 asymptomatic subjects in a 6-year follow-up study. Four age groups were included (40-45, 46-50, 51-55 and 56-60) with the aim of obtaining a random equal number of men and women sample. The baseline IMT ranged from 0.42 to 2.12 mm (mean 0.63 mm, SD 0.14 mm). In 4.66% subjects completing the 6-year follow-up, the IMT decreased by more than 0.1 mm and in 18% there was no significant IMT change (> 0.1 mm). In the remaining individuals (77.33%) the IMT increased by at least 0.1 mm. The IMT increase in the 56-60 age group was significantly higher than in the remaining age groups (p < 0.02). A significantly higher percentage of smokers was also observed in the 56-60 age group (p < 0.05). However, the IMT increase in the smoker subgroups was not significantly different from the mean IMT increase observed in the whole group or from the IMT increase observed in the non-smoker group. Blood pressure variations were not associated with change of IMT over six years. The main difference between the four groups was an average weight 5.7% higher in the oldest age group at the end of the study (4.44% higher at inclusion). In conclusion the increase in IMT appeared to be greater in older subjects and the effect of smoking did not apparently affect IMT increase. The method of IMT measurements is able to demonstrate the age-related evolution of intima-media in a population.