This study examined the predictive relationship between adult literacy students' reading assessments in four component sub-skills (phonological decoding, vocabulary, fluency, and spelling) and their gains in reading comprehension from pretest to posttest. Additionally, the adult literacy instructors' content knowledge in reading instruction and their ability to apply this knowledge was analyzed to determine if there was a relationship between these factors and student reading comprehension gains. Lastly, students' age was analyzed to determine if this factor predicted reading comprehension gain and whether it interacted with any of the other predictor variables. Assessments were given to 139 adult literacy students and their ten instructors. Results showed that students' skills in phonological decoding and vocabulary were significant predictors of gains in reading comprehension. Teacher knowledge about fluency instruction, vocabulary instruction, and reading comprehension instruction were also significant predictors of gains in reading comprehension. These results show that these student and teacher variables predicted the extent of improvement in reading comprehension for the adult literacy students. These two sets of findings when combined reveal that all of the reading components play an important role in reading comprehension. As such, the present study's findings suggest that professional development for teachers, and reading instruction for intermediate level adult students, should address all four reading components. The instructional focus should be influenced by results of careful student assessment in the components of reading. In the current atmosphere of heightened teacher and student accountability, as well as increased academic rigor required by the Common Core Learning Standards, adult education teachers will need to be as well trained and prepared as K-12 teachers. Lastly, age was found to be related to gains in reading comprehension and showed a curvilinear, U-shaped function. Students in the mid range in age (i.e., 40 to 53 years) improved less in reading comprehension than both younger and older students. In addition, age was related to performance on the fluency measure such that older students showed a decline in their speed to identify separate words in rows of letters than younger students. [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.]