Physical inactivity is a worldwide pandemic associated with major chronic diseases. Given limited resources, policy makers are in need of physical activity interventions that provide best value for money.; To summarize evidence from RCT-based economic evaluations of primary prevention physical activity interventions in adult populations outside the workplace setting.; Systematic review of health economic evaluations. Incremental cost-effectiveness ratios (ICERs) in US$ per MET-hour gained were estimated on the basis of mean differences in intervention costs and standardized effects between intervention and control groups.; Identification of relevant studies via systematic searches in electronic databases (MEDLINE, Embase and NHSEED).; Cost-effectiveness analyses in which all data (except unit costs) came from one RCT investigating physical activity interventions for primary prevention or health promotion in an adult population in high-income countries.; In twelve eligible studies, 22 interventions were investigated. Interventions were based on advice, goal setting and follow-up support, exercise classes, financial incentives or teaching on behavioral change. The ICER varied widely among the interventions and four interventions showed an ICER below the applied benchmark of US$0.44 to US$0.63 per MET-hour gained. These four interventions were based on individualized advice via print or web.; We found evidence from RCTs indicating cost-effectiveness of some physical activity interventions for primary prevention in adults. However, the majority of interventions assessed would not be cost-effective according to the benchmark applied. Furthermore, our study showed that trial-based evidence on cost-effectiveness of physical activity interventions is scarce. Therefore, we recommend that future studies investigating the efficacy or effectiveness of such interventions consider costs as an additional outcome and assess cost-effectiveness.