This study aimed to ascertain by means of a new scale older adults' motives for engaging in physical activity, in a probability and representative sample of an older urban population. The sample size was 630 older adults, ranging from 65 to 94 years in age, randomly selected using multistage sampling. The participants completed a 17-item questionnaire, as well as answering questions on demographic variables, type of demand for physical activity, and physician's recommendation. A principal-component analysis was performed. The relationships among the four factors (physical health, social relationships, competence, and physician's advice) show a clearly motivational structure. Significant relationships have also been found between physician's recommendation and type of demand. The findings suggest that programs promoting physical activity in older adults should have different characteristics from those aimed at general adult populations.