Objective . To analyse patients ' self-reported reasons for not adhering to physical activity referrals (PARs). Design and setting . Data on 1358 patients who did not adhere to PARs were collected at 38 primary health care (PHC) centres in Sweden. Intervention . PHC providers issued formal physical activity prescriptions for home-based activities or referrals for facilitybased activities. Subjects . Ordinary PHC patients whom regular staff believed would benefi t from increased physical activity. Main outcome measure: Reasons for non-adherence to PARs: " sickness " , " pain " , " low motivation " , " no time " , " economic factors " , and " other " . Results . Sickness and pain were the most common motives for non-adherence among older patients. The youngest patients blamed economic factors and lack of time more frequently than those in the oldest age group. Economic factors was a more common reason for non-adherence among those referred for facility-based activities compared with those prescribed home-based activities. Low motivation was a more frequent cause of non-adherence among those prescribed home-based activities compared with those referred for facility-based activities. Furthermore, lack of time was a more common reason for non-adherence among patients issued with PARs due to high blood pressure than other patients, while low motivation was a more common reason among patients issued with PARs because of a BMI of Ͼ 25. Conclusion . The reasons for non-adherence differ between patients prescribed home-based activities and referred for facility-based activities, as well as between patients with different specifi c characteristics. The information obtained may be valuable not only for the professionals working in PHC, but also for those who work to develop PARs for use in different contexts.