OBJECTIVES: To estimate the number of patients and costs for the treatment of selected diseases in Switzerland, depending on physical activity level. Calculation of accidents due to sport or other causes. METHODS: Top-down approach, modeling the number of cases and deaths due to coronary heart disease (CHD), hypertension, non-insulin-dependent diabetes (NIDD), mammary cancer, colon cancer, lower back pain (LBP), brief recurrent depression, osteoporosis. Distinction by activity level (active or not). Decision tree model for calculating the number of accidents, disability, and deaths due to sports and general accidents. Inclusion of direct costs, indirect costs, and transfer payments. A comparison of disease and accident costs was not possible, because accidents could not be separated by activity level. RESULTS: The burden of disease is 8.5 billion SFr in direct and 6 billion SFr in indirect cost. The inactive population (37%) incurs most of the direct costs (49%, 4.14 billion SFr). Diseases occurring in the active population (61%) require 2.7 billion SFr a year. Each physically inactive person costs 2,595 SFr per year; active people 1,700 SFr per year. The risks attributable to physical inactivity are: CHD 24%, hypertension 15%, NIDD 24%, mammary cancer 12%, colon cancer 25%, LBP 12%, depression 44%, osteoporosis 27%. The proportion of costs for diseases caused by physical inactivity is 16%. Total number of general accidents is 670,000, plus 299,000 sports-related accidents. 1,875 accident-related deaths occur, with only 161 (9%) of them caused by sport. The ratio of the yearly direct costs of non-sport /sport-related accidents is 3.4 / 1.1 billion SFr, and the ratio of indirect costs is 6.3 / 2.3 billion SFr. Transfer costs for disability payments are 37 million SFr per year (86% for non-sport accidents). CONCLUSIONS: Promotion of physical activity is cost saving in terms of disease costs. Our findings regarding the disease costs per patient are consistent with recently published results for the US.