Exercise-related public health recommendations and research for increased fitness and health had long focused on vigorous exercise or the lack thereof. Recently scientific interest in possible effects of sedentary behaviour (SB) (sitting) independent of moderate-vigorous intensity exercise has been growing.We conducted a selective literature search in Pubmed and the Sedentary Research Database with the outcomes SB, risk factors, mortality and morbidity in adults. We included only reviews and systematic reviews.Observational studies suggest an association between SB and all-cause and cardiovascular, but not cancer mortality. SB also seems to be associated with diabetes and overweight/weight gain. Evidence for other diseases, such as cardiovascular diseases, hypertension, cancer, and mental diseases is limited also because of the heterogeneity and poor methodology of the -studies. Intervention studies found inconsistent evidence that SB is associated with detrimental effects on markers of cardiometabolic risk.The evidence on the detrimental effects of sedentary behaviour is decreasingly convincing with the endpoints of mortality, -morbidity, and markers of metabolic risk, in that order. Higher TV and screen time, but not total SB seems to be associated with higher all-cause and cardiovascular, but not cancer mortality. Further intervention studies are needed to establish -dose-response relationships and potentially protective effects of cardiorespiratory fitness and physical activity.