This research examined opposing motivational processes produced by competition in vivo. Participants (N = 115) were randomly assigned to competition or no competition conditions, and completed a risk behavior measure (the Columbia Card Task). Cardiovascular responses were monitored during performance to assess challenge (approach-motivated) and threat (avoidance-motivated) states. Competition participants exhibited more sympathetic arousal than controls, but no main effects of competition emerged for the motivationally tuned cardiovascular measures or risk outcomes. Instead, consistent with the opposing processes model, within the competition condition some participants were approach-oriented (as indicated by challenge-type physiological responses), whereas others were avoidance-oriented (as indicated by threat-type physiological responses). Moreover, participants who exhibited a challenge pattern of physiology reactivity were more risk-seeking than participants who exhibited a threat pattern of reactivity. Findings are discussed in the context of existing work on competition and risk, and the opposing processes model of competition.