We examined the growth of the right common carotid artery of young rabbits after ligating the left common carotid artery at 3 weeks of age, a procedure that approximately doubled right carotid blood flows. Flow increased from 0.065 ± 0.003 to 0.096 ± 0.009 ml/s within 1 h and, at 15 weeks of age, carotid blood flows in experimental animals (0.747 ± 0.102 ml/s) were more than double of those of sham-operated control animals (0.334 ± 0.053 ml/s). Contralateral carotid ligation resulted in more rapid increases in diameter of the artery with growth in the experimental animals. At 15 weeks of age, the vessel was 15% larger than that of sham-operated controls (2.70 ± 0.09 vs. 2.34 ± 0.05 mm). This more rapid growth of diameter resulted in shear stresses that were not different from controls despite the higher blood flow rates. Interestingly, however, shear stresses in control arteries fell from 17.4 ± 3.4 to 9.19 ± 1.16 dyn/cm<sup>2</sup> over the experimental period (p < 0.05). Elastin accumulation in the experimental artery was much more rapid than in controls and elastin contents were 49% more than in controls at 15 weeks of age. DNA and collagen contents were not significantly affected by contralateral carotid ligation. Previously, we found that experimental manipulations that decreased flow in the same artery of weanling rabbits substantially affected elastin and DNA accumulation, but had no effect on collagen contents. We conclude that increased blood flow is associated with arterial growth and specifically with accumulation of elastin, a wall constituent that bears much of the wall tension at resting blood pressure, and therefore is a primary determinant of resting vessel dimensions.