Three studies are reported that show that health-relevant information (e.g., blood pressure [BP] or symptoms) initiates an active cognitive search process that results in the construction of an illness representation. Study 1 showed that informing subjects that their BP was elevated affected two attributes of illness representation: identity (label and symptoms), and time line or expected chronology of the health threat. Subjects given a high-BP reading reported symptoms commonly associated with high BP, especially if they attributed the high-BP reading to stress. Study 2 showed that the active search process uses causal information (a third attribute of representations) to give meaning to symptoms. Specifically, subjects used environmental cues to interpret whether familiar, unfamiliar, and ambiguous symptoms were due to illness or to stress. In Study 3 we showed that the constructive process, initiated by a high-BP reading, is directed by prior beliefs about the time line for developing high BP and by the presence of external cues about the stressfulness of the subject's daily life. Subjects who believed BP was labile and that they were under high daily stress or who believed BP was stable and that they were under low daily stress reported more symptoms. The significance of these findings for understanding how people process diagnostic labels and symptom information involved in the construction of illness representations is discussed.