While there is much evidence that health knowledge supports understanding of health texts, little is known about the processing mechanisms underlying this effect. We used the moving window paradigm to examine attentional allocation to reading health and domain-general texts among older adults with hypertension who varied in verbal ability (general knowledge) and health knowledge. More knowledgeable readers allocated less time to word-level processing and more to conceptual integration. Domain knowledge further engendered earlier conceptual integration in the health texts, as measured by differential allocation to intrasentence integration but less at the end of the sentence compared to less knowledgeable readers. This suggests that knowledge gave readers a head start in building a textbase representation of the ideas conveyed by the sentence. Thus, knowledge helped structure comprehension by supporting conceptual integration. Implications for the design of patients' education materials are discussed.