Despite the widespread use of the term "impulsivity in virtually every field of psychology, the concept is both poorly defined and misunderstood. Beyond some general reference to reduced impulse control, considerable ambiguity surrounds what exactly is meant by "impulsive. The ambiguity has largely arisen from disagreement concerning the processes that cause this rapid, spontaneous, excessive, and unplanned behaviour. The aims of the present paper are to (a) provide a critical review of the current way in which psychologists conceptualise and measure impulsivity; (b) provide a framework (a three-tiered conceptualisation of impulsivity) for a revised and clarified conceptualisation; and (c) make recommendations, using this framework, for future impulsivity research and practice. It will also be demonstrated that impulsivity, as it is presently conceptualised, is not a construct, rather a behavioural outcome of several distinct constructs. Recommendations for future empirical explorations of impulsivity include a shift toward specific causal explanations presumed to underlie such behaviour, and valid and reliable quantification of impulsive behaviour and its causal mechanisms. Clinical implications of the three-tiered conceptualisation are discussed.