The purpose of the present study was to estimate the association of physical activity level (PAL) with metabolic syndromes among the employed population in China. Using data from the 2002 China National Nutrition and Health Survey, the PAL of 21 834 subjects aged 18-59 years was described, and its relationship with the risk of metabolic syndrome was studied after adjusting for the relative effects of smoking, drinking, diet and socioeconomic status. Information on physical activity was collected by trained investigators using a 1-year physical activity questionnaire. PAL was classified into four categories: sedentary (PAL 1.00-1.39), low active (PAL 1.40-1.59), active (PAL 1.60-1.89) and very active (PAL 1.90-2.50). The definition of metabolic syndrome by the International Diabetes Federation 2005 was applied. The percentage of people being sedentary, low active, active and very active was 12.3%, 13.7%, 20.1% and 53.9% respectively. The crude prevalence of metabolic syndrome in the sedentary, low active, active and very active groups was 9.7%, 6.9%, 5.6% and 4.9% respectively. After adjusting for the effect of other risk factors, the higher the PAL, the lower the relative risk of metabolic syndrome as well as the individual metabolic abnormalities. The risk of overweight/obesity and metabolic syndrome was 50% and 59% less, respectively, in the adults who were very active and whose dietary fat contributed less than 20% to energy intakes when compared with their counterparts who were sedentary and consumed more fat (> or = 30% energy). PAL was an independent risk factor for obesity and multiple metabolic syndrome abnormalities among the employed population in China. The high-risk population were middle-age males living in large cities with high incomes who drink alcohol.