Global virtual teams are internationally distributed groups of people with an organizational mandate to make or implement decisions with international components and implications. They are typically assigned tasks that are strategically important and highly complex. They rarely meet in person, conducting almost all of their interaction and decision making using communications technology. Although they play an increasingly important role in multinational organizations, little systematic is known about their dynamics or effectiveness. This study built a grounded theory of global virtual team processes and performance over time. We built a template based on Adaptive Structuration Theory (DeSanctis and Poole 1994) to guide our research, and we conducted a case study, observing three global virtual teams over a period of 21 months. Data were gathered using multiple methods, and qualitative methods were used to analyze them and generate a theory of global virtual team dynamics and effectiveness. First, we propose that effective global virtual team interaction comprises a series of communication incidents, each configured by aspects of the team's structural and process elements. Effective outcomes were associated with a fit among an interaction incident's form, decision process, and complexity. Second, effective global virtual teams sequence these incidents to generate a deep rhythm of regular face-to-face incidents interspersed with less intensive, shorter incidents using various media. These two insights are discussed with respect to other literature and are elaborated upon in several propositions. Implications for research and practice are also outlined.