This dissertation is motivated by two problems. First, existing literature characterizes patient handoff as an information transfer activity in which safety and quality are compromised by practice variation. This has prompted a movement to standardize practice. However, existing research has not closely examined how practice variations may be responses to situational and organizational factors or evidence of involved parties accomplishing important functions beyond information transfer. Consequently, standardization efforts run at least two risks: overlooking opportunities for improvement, and engendering negative unintended consequences. Second, despite the fact that roughly 50% of all hospitalized patients are handed off from emergency departments to inpatient units, such handoffs are significantly understudied. I conducted a two-year ethnographic study of handoffs occurring between Emergency Department and General Medicine physicians when patients were admitted to one highly-specialized tertiary referral, teaching hospital. Using theoretical sampling informed by a Grounded Theory methodology, I conducted observations (n=349 hours) and semi-structured interviews (n=48) and recorded handoff conversations (n=48). I analyzed data by means of immersion, various qualitative coding approaches, and memo writing. Findings are organized in three chapters. First, I challenge the dominant model of handoff as information transfer by demonstrating that physicians actively construct understandings of their patients, over time, as they encounter, interpret, assemble, and reassemble information through socially-interactive processes within particular contexts and situations. Consequently, multiple understandings of a single patient are not only possible but likely. Second, I characterize admission handoffs as negotiations, situated by entangled webs of motives and concerns which produce ambiguities. Involved parties must navigate these ambiguities as they develop their differing understandings of patients, resolve conflicts over approaches to care, and agree regarding additional work. Third, I show that boundaries between units are ongoing, effortful accomplishments, re-enacted through interactive negotiations. Over time these negotiations have the potential to shift boundaries and alter the divisions of labor in the hospital, with potential consequences for organizational outcomes. Recommendations for practical improvements and further research are presented. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]