Risk factors for arterial stiffness progression have not been well characterized. We examined the relationship between arterial stiffness progression and body weight and weight gain in a group of healthy young adults. Aortic pulse-wave velocity was assessed at 2 time points approximately 2 years apart in 152 white and black adults aged 20 to 40 years, and was standardized by the time between visits to obtain annualized pulse-wave velocity changes. Blacks had 15.5 cm/s per year larger annual pulse-wave velocity increases compared with whites (P=0.02), even after multivariable adjustment for weight and blood pressure changes. Larger annual pulse-wave velocity increases were also associated with larger baseline body weight (P=0.02), waist girth (P=0.003), and body mass index (P<0.001), and greater annual weight gain (P=0.02), after adjustment for baseline pulse-wave velocity. After multivariable adjustment that included blood pressure changes, larger baseline waist girth (P=0.009), baseline body mass index (P=0.001), body mass index increase (P=0.037), and weight gain (P=0.017) remained significantly associated with larger annual pulse-wave velocity progression. Weight change showed a direct relationship with pulse-wave velocity change; mean annual pulse-wave velocity changes were -29.9 cm/s per year (regression) for those with >or=4.5 kg annual weight loss and 18.2 cm/s per year (progression) for those with >or=4.5 kg annual weight gain. These data show strong associations between weight gain and arterial stiffness progression, as well as between weight loss and arterial stiffness regression. These data greatly underscore the vascular benefit of weight loss. Successful weight loss programs in young adults, particularly blacks, are needed.