Virtual agents, pedagogical agents, social relationships, social dialog, dialog modeling, serious games, simulation-based learning, educational technology, intercultural competence, interpersonal skills training, human-computer interaction. Embodied conversational agents put a “human ” touch on intelligent tutoring systems by using conversation to support learning. When considering instruction in interpersonal domains, such as intercultural negotiation, the development of an interpersonal relationship with one’s pedagogical agent may play a significant role in learning. However, there is conflicting evidence in the literature both regarding the ability of agents to cultivate social relationships with humans, and their effect on learning. In this dissertation, I present a model of social dialog designed to affect learners ’ interpersonal relations with virtual agents, a development process for creating social dialog, and empirical studies showing that this dialog has significant effects on learners ’ perceptions of the