The average amount of time spent sedentary is considerable among all age groups in Denmark and evidence points toward an increasing trend. Based on the current scientific research, sedentary behaviour can be viewed as an independent risk factor for many non-communicable diseases and premature mortality. TV viewing is the most pervasive and common form of sedentary behaviour during leisure time and there is substantial evidence for a detrimental health effect of prolonged TV viewing time. At present, there is insufficient evidence to quantify an upper limit for total sedentary time.