To be ostracized is to be ignored and excluded. How does ostracism affect individuals? Considerable research has now shown that the initial (reflexive) reactions to even the most minimal forms of ostracism are painful and distressing. Fundamental needs of belonging, self-esteem, control, and meaningful existence are thwarted; sadness and anger increase. These effects emerge despite individual differences or situational factors that should lead logically to easy dismissal. With time to appraise the ostracism episode, individuals become differentially sensitized based on (i) the specific needs that are thwarted, (ii) their own individual differences, and (iii) their assessment of who ostracizes and why. These differences lead to need-restorative behaviors that range from being overly socially attentive and susceptible to influence to being aggressive and antisocial.