Following the devastation of World War II, policymakers and scholars worked to advance international partnerships and mutual understanding. In the 1940s and 1950s, international student exchange programs were launched to foster international good will; training programs for diplomats were created that focused on intercultural communication competence; and researchers turned their attention on how to optimize intergroup relations. Most prominently, Gordon Allport outlined principles of effective intergroup contact in the contact hypothesis. Scholarship based on the contact hypothesis later determined that the potential for friendship is not only a facilitating but also an essential factor for prejudice reduction and optimal intergroup contact. Focusing largely on the friendship experiences of international students studying abroad, research also identified numerous other benefits of intercultural-friendship formation, including stronger language skills, greater life satisfaction, lower levels of stress, and enhanced perceptions of the host country. Despite these benefits, the lack of friendship between sojourners and host nationals is a common finding in intercultural-friendship research and a concern for the many educational institutions worldwide that are attempting to internationalize, in part by attracting international students. Current research, therefore, often focuses on factors that influence intercultural-friendship formation and, increasingly, on measures for promoting intercultural friendship. First among the factors affecting the development of intercultural friendships is cultural difference. Cultural similarity provides attributional confidence and reduces uncertainty; that is, interactants can more easily predict and explain behaviors in people who are similar to them. Highly dissimilar cultures often exhibit differences in communication patterns, value dimensions, and friendship styles that can impede relationship development, especially in the orientation and exploratory stages of social penetration, during which cultural complexities are most critical. Another prominent factor is the interactants’ motivation to form relationships across cultural lines. In one of the prime arenas for intercultural contact, international student exchange, for example, sojourners seeking cultural knowledge and personal growth generally have more interest in interaction and friendships with host nationals than students who are task oriented and focus on education for better career prospects after returning home. Similarly, host environment factors, such as host receptivity (ranging from welcoming attitudes to discrimination) influence the likelihood with which intercultural friendships are formed. Other factors affecting intercultural-friendship formation include communicative competence, intercultural sensitivity, and aspects of identity and personality (e.g., cultural versus personal identification, empathy, and open-mindedness). Among measures for promoting intercultural-friendship formation are infrastructures that facilitate proximity and frequency of contact, provide foreign language training, support experience abroad, and offer intercultural education and training to further intercultural competence and the appreciation of difference.