Given the understanding of the importance of interaction in second language learning, and lack of research on the nature and types of interactivity in hypertext for English-as-a-second-language (ESL) learning, this study addresses the following questions: What is interactivity in ESL hypertext development? What types of interactivity are incorporated into the hypertext of current Word Wide Web sites devoted to ESL learning? What authoring strategies and techniques are available to optimize the incorporation of interactivity in ESL hypertext? Data is collected from approximately 30 ESL Web sites and their authors for content analysis. A taxonomy of interactivity is developed based on related literature review, and on findings from the content analysis of this study. The taxonomy covers four categories: perceptual, cognitive, cultural, and technological. Each category further branches off into several subcategories. The taxonomy is intended to provide a framework for identifying and evaluating interactivity in hypertext for ESL learning.