It is essential to provide high quality interventions designed to improve struggling readers' reading comprehension while making use of limited resources. This study explored, through an holistic, multiple-case study design, volunteer-student interactions and activities in an after school reading program utilizing minimally-trained volunteers. The purpose of this research was to explore and describe factors that differentiated the volunteers working with students who made larger or smaller gains in reading comprehension. The participants in this study were four minimally trained community volunteers and three fourth grade students who were identified as at-risk for meeting basic standards for reading comprehension. The activities and interactions that the volunteers and students engaged in were the main focus of study. These included time spent reading text, comprehension promoting activities (e.g., encouraging understanding of language, understanding of words, and use of comprehension strategies), scaffolding and modeling, providing information, questioning, and giving feedback. The volunteers working with the students who made large reading comprehension gains spent more time reading text (around two-thirds of their session), more consistently practiced a variety of comprehension strategies, and provided a higher ratio of positive to negative feedback. The time that the volunteer spent reading text differentiated the high-gains from the low-gains case, with more volunteer reading, but the time that the student spent reading did not distinguish the pairs. The volunteer working with the student who made little gain in reading comprehension spent less time reading text, about half of the session. This pair practiced a limited variety of comprehension strategies, and engaged in more instructional management. When interacting with the student, this volunteer directly provided information more often than the volunteers from the high-gains cases. This volunteer also provided a higher ratio of negative to positive feedback. The results of this study are limited by potentially confounding variables including text difficulty and student ability. This research suggests a need for a larger-scale study of factors related to the influence of community volunteers on students' reading comprehension. This research might examine the factors that were related to gain or lack of gain in reading comprehension in these cases. [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.]