The sensation seeking scale (SSS-V, Zuckerman et al., 1978) has been shown to be a valid and reliable instrument for identifying individuals with the propensity or desire to engage in so-called sensation seeking activities.The SSS-V does not measure motives for engagement in high-risk sport and cannot be used for such a purpose. Recent research has focused on emotion regulation and agency as motives for participation in high-risk sport and has highlighted the need for a domain-specific measure of them as motives for participation in high-risk sport (see, for example,Woodman et al., 2010). The present paper reports two studies that chart the development of a measure of Sensation Seeking, Emotion Regulation, and Agency (the SEA scale) as motives for participation in high-risk sport. The measure consists of three separate questionnaires rating participants' percepts and experiences across three time points: between participations, during participation, and after participation.The between participations questionnaire measures three factors: need for sensations; difficulty regulating emotions; and diminished agency.The while participating questionnaire measures three factors: experience of desired sensations; experience of intense emotions; and agentic experience. The after participating questionnaire originally also measured three factors, but confirmatory factor analysis suggested that these could be just two factors: satisfaction of need for sensations; and transfer of agentic collapsed to emotion regulation. The final SEA scale consists of three, 18-item questionnaires that demonstrate good model fit, adequate internal consistency, and good alpha reliability levels.