Cigarette smoking is associated with impaired arterial function as measured by reduced vasodilation in response to reactive hyperemia. However, previous studies did not account for potential differences in shear stimuli. The purpose of this study was to use young, occasional smokers to ethically evaluate the effects of acute and chronic smoking on shear rate-diameter dose-response slopes. Young (20 to 26-y-old) nonsmokers (n = 9) and occasional (<1 pack/week) smokers were tested (n = 9). Smokers were tested after abstaining for 2 or more d and then immediately after smoking two cigarettes. Shear rate was manipulated using five upstream ischemic durations (0.5, 1, 2, 5 and 10 min). Radial artery blood velocities and diameters were assessed using Doppler ultrasound. Hierarchical linear modeling (HLM) was used to estimate change in diameter using repeated measures of shear rate nested within each subject. The shear rate-diameter slope was reduced by 35.9% in occasional smokers compared with nonsmoking controls (beta = 2.78(10-4) versus 1.78(10-4), p = 0.004). Acute smoking further attenuated the shear rate-diameter slope (i.e., arterial function) by 23.8% (beta = 1.79(10-4) versus 1.36(10-4), p = 0.037). These results suggest that repeated bouts of occasional cigarette smoking can chronically attenuate arterial function in otherwise healthy, young persons.