1. Atherosclerotic changes of the coronary vascular wall include localized plaque formation and diffuse hardening, both of which influence tensile strength of the inner vascular wall. Insight into the relation between age, the atherosclerotic process and vessel wall elasticity may contribute to the prevention of secondary vascular wall damage. 2. To evaluate the determinants of coronary artery wall elasticity, we studied a group of 34 patients, aged 54.6 +/- 10.1 years, who underwent balloon angioplasty for coronary artery disease. With the use of 30 MHz intravascular ultrasound, a total of 127 cross-sections of coronary artery segments outside the balloon area were studied. The echographic appearance of the intima was classified as normal intimal thickening, fibrous lesions and calcified lesions. Fibrofatty lesions, which are believed to be rupture prone, were analysed separately. From the lumen area change, measured by semiautomated planimetry from digitized ultrasound images, and simultaneously measured aortic pressure change during the diastolic phase of the cardiac cycle, two elastic parameters were derived, pressure-strain modulus Ep and beta-stiffness. 3. In univariate analysis Ep and beta-stiffness were determined by age, vessel size, intimal composition, severity of lumen obstruction and gender, but not by eccentricity of the lesion or a specific coronary artery. In multivariate linear analysis, increased vessel wall stiffness was independently determined by advanced age, larger vessel size, intimal composition, and to a lesser extent by female gender. Elastic parameters of fibrofatty lesions were not different from other fibrous lesions. 4. Coronary artery wall elasticity is independently determined by age, vessel size and intimal composition.