Sensemaking tasks are challenging and typically involve collecting, organizing and understanding information. Sensemaking often involves a handoff where a subsequent recipient picks up work done by a provider. Sensemaking handoffs are very challenging because handoffs introduce discontinuity in sensemaking. This dissertation attempts to explore various factors involved in sensemaking handoffs. This work drew on existing literature on sensemaking to propose five sensemaking task attributes: representation novelty required, encoding difficulty, broader applicability, representation search space and subtask interdependence. These attributes capture what makes sensemaking difficult and also help in choosing tasks to study sensemaking as well as modifying laboratory tasks so that they involve more sensemaking. Synthesizing existing literature on collaboration, the dissertation identified important elements in a sensemaking handoff: intent to collaborate, common ground, shared space, awareness, additional communication and handoff artifacts. These make up an ecology that helps deal with challenges of sensemaking expressed by the attributes of sensemaking tasks. A study of sensemaking handoffs in computer-support helpdesks found that sensemaking handoffs could be successful, especially when various collaboration elements complement handoff materials. The study also raised questions about the quality and utility of handoff material from incomplete sensemaking, and about the timing of handoffs. Three lab-studies conducted in the dissertation provided insights regarding the role of artifacts in sensemaking handoffs. The first study confirmed that handoff can be as effective as simultaneous collaboration. The second lab-study suggests that the quality of the handed-off material was important. Poor quality material seemed to be used at different times and in different ways from good quality material. The third lab-study found that available structure in the form of websites as well as handoff artifacts can have an effect on sensemaking. When external structure was available people adapted and used it early on. People appropriated structure sooner from the handoff artifacts when structure was not easily available externally, as compared to when structure was easily available externally. Artifact maturity was also found to have an effect; artifacts from late stages that were placeholders for structures in a task were used more often and were rated higher by the recipients. [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.]