Social exclusion can have profound effects on a vast array of motivated psychological processes, from social withdrawal and aggression to prosocial behavior and social affiliation. The current studies examined motivationally tuned endocrinological consequences of exclusion by measuring the release of progesterone, a hormone that reflects an individual's level of social-affiliative motivation. Results from two experiments indicate that release of progesterone following social exclusion depends on people's levels of social anxiety and rejection sensitivity. Individuals high in social anxiety displayed a drop in progesterone in response to exclusion, a pattern consistent with a lack of affiliative motivation. In contrast, individuals high in rejection sensitivity displayed an increase in progesterone when given an opportunity to reaffiliate, a change consistent with a desire for compensatory social contact. These findings provide new insight into the immediate biological changes precipitated by social exclusion--changes that could initiate a range of motivated social responses.