Study question Do trials of physical activity promotion based in primary care show sustained effects on physical activity or fitness in sedentary adults, and are exercise referral interventions more effective than other interventions?Summary answer Trials of physical activity promotion based in primary care show positive effects on physical activity levels, but not on fitness, over at least 12 months; however, not enough evidence exists to indicate whether exercise referral is more effective than other primary care interventions.What is known and what this paper adds Physical activity promotion in primary care, including exercise referral, is reported to improve physical activity levels in the short term but its longer term effect was unclear. Our review found that promotion of physical activity to sedentary adults identified through primary care significantly improves self reported physical activity levels over at least 12 months; we found few trials of exercise referral interventions with 12 months’ follow-up and more trials are needed to determine their relative effectiveness.