It is well established that physical activity level is inversely associated with cardiovascular morbidity and mortality, and with all-cause mortality. However, the dose-response relationship between physical activity and other cardiovascular disease risk factors is not fully understood. The aim of the present study was to explore the dose-response relationship between daily physical activity, as measured by a metabolic equivalent score, and BMI, waist circumference, waist hip ratio, total cholesterol, HDL, LDL, triglycerides, systolic and diastolic blood pressure. A total of 1693 men and women, 33-64 years of age, from the 3 year follow-up of a population-based intervention study, were included in this cross-sectional study. Information on physical activity and other lifestyle factors was obtained by self-report questionnaire. Associations between activity level and biological variables were explored by general linear regression. Data from 835 (51%) men and 805 (49%) women were included. Mean age was 50.8 years (33-64). A significant inverse association between average 24-hour physical activity level < or =45 METs and waist circumference (men p = 0.012, women p = 0.011), BMI (p = 0.0004), waist-hip-ratio (p = 0.002) and triglycerides (p = 0.0001) was found as well as a positive association with HDL (p = <0.0001). In those with an activity level above 45 METs there were no associations. No association was found with total cholesterol, LDL, systolic or diastolic blood pressure. This study suggests a linear dose-response relationship between activity level and certain biological cardiovascular risk factors up to a threshold of a daily 24 h MET-score of 45, which corresponds to a moderate physical activity level.