Measurement of sedentary behaviours in surveillance systems and in population studies involves the use of subjective and objective methods. Subjective methods have traditionally included questionnaires to provide a snapshot of sedentary behaviours and to quantify the time spent in sedentary behaviours as categorised by energy expenditure and posture. New horizons for subjective methodologies include smartphone applications that allow measurement of the facets and subcategories of the Consensus Taxonomy of Sedentary Behaviours. Objective methods have used pedometers to determine the proportion of the populations with <5000 steps/day as defined by the step-defined Sedentary Behaviour Index and accelerometers to determine the time spent in sedentary behaviours defined as <100 acceleration counts per minute. New horizons for objective methodologies include integrated motion and posture sensors to assess time spent in metabolic intensities ≤1.5 metabolic equivalents (METs) and sitting or reclining postures. Innovative ways to score accelerometer outputs to allow pattern recognition of types of sedentary behaviours also are on the horizon. Selection of a sedentary measurement method should include considerations of the validity, reliability and responsiveness of a method to reduce measurement error. Methods also should be selected that allow evaluation of Hill's Criteria for Causality to advance the understanding of the effects of sedentary behaviours on health outcomes.