The United States' aging population increasingly requires the medical community to address chronic disease management, rather than the treatment of acute conditions. Management of long term health concerns relies heavily on the active participation of the patient, yet insight into patient motivations is lacking. A review of the literature revealed that most medical research into the patient as a person has addressed factors related to non-compliance, such as demographics, compliance with specific therapeutic regimens, and external factors such as pill shape and color. Research into the health decision-making process from the perspective of the patient was found to be generally absent in the literature.;In an effort to reduce that void, 21 people diagnosed within the past six months with Type 2 diabetes met with the researcher three times over a period of six months and were interviewed as to the factors that were influencing their decisions to make changes to their lifestyle in response to diabetes. Analysis of the data generated by these interviews revealed four categories that influenced health decision-making. These factors that emerged were (a) the degree of emotional upset, termed disequilibrium following their diagnosis with diabetes; (b) varying knowledge about their illness that could be described as factual knowledge, emotional knowledge, and experiential knowledge; (c) differing perceptions of empowerment over their illness, broadly categorized as self-agency; (d) and the sense of purpose that inspired their efforts toward change.;The interrelationships among these categories are presented as a theory of health decision-making, grounded in the perspective of the patient. The new theory is compared with existing explanations for health decision-making. The paper ends with a discussion about the implications of these findings for healthcare professionals, the limitations of naturalistic research, and suggests directions for future study.