In this qualitative study focus groups were used to gain an in-depth understanding of personal and social influences on physical activity in 48 52-87-year-old participants. A model produced using a Grounded Theory analysis showed that preventing health decline was particularly important in determining physical activity participation. Other influences included enjoyment of exercise, others as motivators to exercise and perceived limited appreciation for older people's needs. The results are discussed in relation to health and exercise interventions designed to motivate exercise behaviour in older adults.