ABSTRACT. Background and aims: This study aimed at examining the association between unhealthy lifestyle in young age, midlife and/or old age and physical decline in old age, and between chronic exposure to an unhealthy lifestyle throughout life and physical decline in old age. Methods: The study sample included 1297 respondents of the Longitudinal Aging Study Amsterdam (LASA). Lifestyle in old age (55-85 y) was assessed at baseline, whereas lifestyle in young age (around 25 y) and midlife (around 40 y) were assessed retrospectively. Lifestyle factors included physical activity, body mass index (BMI), number of alcohol drinks per week and smoking. Physical decline was calculated as a change in physical performance score between baseline and six-year follow-up. Results: Of the lifestyle factors present in old age, a BMI of 25-29 vs BMI <25 kg/m2 (OR=1.6; 95% CI: 1.1-2.2) and a BMI of ?30 vs BMI <25 kg/m2 (OR=1.8; 95% CI: 1.2-2.7) were associated with physical decline in old age. Being physically inactive in old age was not significantly associated with an increased risk of physical decline, although, being physically inactive in both midlife and old age increased the odds of physical decline in old age to 1.6 (95% CI: 1.1-2.4), compared with respondents who were physically inactive in midlife and physically active in old age. Being overweight in both age periods was associated with an OR of 1.5 (95% CI: 1.1-2.2). Conclusions: These data suggest that overweight in old age, and chronic exposure to physical inactivity or overweight throughout life, increases the risk of physical decline in old age. Therefore, physical activity and prevention of excessive weight at all ages should be stimulated, to prevent physical decline in old age.