Obesity in middle and old age predicts mobility limitation; however, the cumulative effect of overweight and/or obesity over the adult life course is unknown. The association between overweight and/or obesity in young, middle, and late adulthood and its cumulative effect on incident mobility limitation was examined among community-dwelling US adults aged 70-79 years at baseline (1997-1998) in the Health, Aging and Body Composition Study (n = 2,845). Body mass index was calculated by using recalled weight at ages 25 and 50 years and measured weight at ages 70-79 years. Mobility limitation (difficulty walking 1/4 mile (0.4 km) or climbing 10 steps) was assessed semiannually over 7 years of follow-up and was reported by 43.0% of men and 53.7% of women. Men and women who were overweight or obese at all 3 time points had an increased risk of mobility limitation (hazard ratio = 1.61, 95% confidence interval: 1.25, 2.06 and hazard ratio = 2.85, 95% confidence interval: 2.15, 3.78, respectively) compared with those who were normal weight throughout. Furthermore, there was a significant graded response (P < 0.0001) on risk of mobility limitation for the cumulative effect of obesity in men and overweight and/or obesity in women. Onset of overweight and obesity in earlier life contributes to an increased risk of mobility limitation in old age.