Patients need support to help them organize and manage the vast amount of health information they now receive, particularly in their increasingly active roles. Clinicians can be frustrated by the perceived failure of patients to use the information given to them, and patients express frustrations with the daunting organizational task of their health information. Yet, few studies have examined the barriers that patients face in organizing and thus effectively retrieving and using their health information. In this paper, we report on a qualitative, longitudinal field study of cancer patients in-situ organizing behavior where we uncovered four types of barriers to organizing: emotional, scalable, temporal, and functional. We provide detailed suggestions for how these barriers could be reduced by either technological or social changes. Our analysis of barriers provides empirical guidance for health-information providers, technology designers as well as patients and their caregivers.