Based on social identity theory (Tajfel & Turner, 1979) we examined the motivational consequences of intergroup status differences as a function of the legitimacy of these differences. Motivational responses were conceptualized in terms of challenge and threat and operationalized by their cardiovascular markers, as described by the biopsychosocial model of challenge and threat (BPS-CT; Blascovich & Mendes, 2010). Participants (N = 104) were categorized in minimal groups. Group status and status legitimacy were manipulated in the context of an intergroup competition. High status elicited relatively more challenge (less threat) when status differences were legitimate than when they were illegitimate. Low status elicited relatively less threat (more challenge) when status differences were illegitimate than when they were legitimate. Cardiovascular reactivity in line with challenge mediated performance during the competition. Results are discussed in terms of the relationship between social status and stress, and the BPS-CT as novel and useful motivational framework for studying social identity processes.