Social connections are fundamental to our existence. As a result, social exclusion is a painful and distressing experience. When belonging is thwarted, people seek inclusion which can be achieved through group membership. Thus, excluded individuals and/or those whose need to belong is particularly strong will be particularly motivated to join groups. Moreover, to the extent that the need to belong is satisfied by closeness with other group members, and closeness is a feature of group cohesion, excluded individuals or ones with a strong need to belong are likely to be attracted to highly cohesive groups. Finally, the subjective importance of a group to its members should determine the degree of perceived cohesion. Importance of a group is defined as the group's centrality to individuals' social identity. The more central a given dimension is to one's identity, the greater the attraction to individuals sharing that dimension (Byrne, 1961). Hence, the more important the group, the greater the attraction of the members to each other, defining group cohesion. Ultimately then, the greater the individuals' prior experience of exclusion or the greater their need to belong, the greater their motivation should be to join important (vs. less important) groups. These notions are investigated in the present dissertation. A review of the literature on social exclusion and the similarity-attraction hypothesis is presented followed by two studies showing that, both in the lab and in the real world, individuals who have been socially excluded want to join and/or feel more connected to important groups.