This research study had two purposes, (a) to design and develop a Web-based learning environment that supports the use of a set of reading strategies, and (b) to investigate the impact of this Web-based learning environment on readers' "memory" and "understanding" of an instructional unit on the human heart (Dwyer & Lamberski, 1977). These purposes led to four major research goals: 1. Guide the design of a Web-based learning environment that supports the use of a set of five reading strategies: (a) "Text-macrostructure" or "chunking" strategy: Readers can chunk the instructional unit on the human heart into smaller sections by moving elements (one or more paragraphs of text and an image) that make up the instructional unit into tabs that they create in the Web-based learning environment. (b) "Summarization" strategy: Readers can write a summary for each section that they create. (c) "Imagery" strategy: Readers can select an image from a library of images that is most representative of the contents of a given section. (d) "Reading self-assessment" or "comfort-meter" strategy: Readers can mark on a scale of 1-5 how comfortable they feel with their understanding of each section of the instructional unit. (e) "Note-taking" strategy: Readers can take notes on an element-by-element basis--these notes are attached to the elements that make up the instructional unit. 2. Establish validity and reliability of Web-based measurement instruments that were designed to measure memory and understanding of the instructional unit on the human heart at four levels of knowledge representation--"micro-textbase," "macro-textbase," "micro-situation model" and "macro-situation model." 3. On the basis of these measurement instruments, determine whether participants who read the instructional unit on the human heart in the Web-based learning environment developed better "memory" and "understanding" of the instructional unit when compared with participants who read the same text on a regular Web page. 4. Develop an understanding of participants' use of the five reading strategies in the Web-based learning environment and their experience in the Web-based learning environment. A design-based research framework guided a series of studies that addressed these research goals. These studies were conducted in four phases. Findings from each of the first three phases of the investigation were used to inform and update the design of the Web-based learning environment, the Web-based measurement instruments, and the research design of the subsequent phase. The investigation culminated in a large-scale quasi-experimental study. [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.]