Biomechanical properties of the coronary arteries were studied according to age and localization of the vascular segment. Experiments were conducted on the proximal and distal segments of the right coronary artery and the anterior descending branch of the left coronary artery in 58 males who ranged in age from 15 to 83 years. Vascular segments prestretched in the longitudinal direction experience an inner pressure of 0 to 240 mm Hg. The main parameters of the mechanical properties of the coronary arteries were determined. Changes in these properties were most marked in the proximal part of the left coronary artery, the deformative capacity of its walls in the circumferential direction being diminished by the end of the fourth and the beginning of the fifth weeks. The right coronary artery experiences less changes than the left coronary artery.