The purpose of this study was to examine the effects of four instructional methods - context clues, definition, elaboration technique, or word parts and word families on the vocabulary growth and acquisition of adults enrolled in a community college developmental reading course. The study investigated whether performance in any or all of the four instructional methods was moderated by age or language. Seventy three respondents participated in the study. Participants were enrolled in one of five sections of College Reading Preparatory II (REA0002) offered in the Spring of 2009 at Indian River State College in Fort Pierce, Florida. All five sections of REA0002 were taught by the same professor, a tenured faculty member, chair of the developmental reading department and Associate Professor of Developmental Reading at Indian River State College. The instruction and tests in all five sections of REA0002 were consistent with the research design which insured continuity and consistency in the use of the four instructional methods. All participants received the same treatment and quizzes. During the course of the study, participants first received a pretest, then the treatment or instruction, followed by an instructional quiz, and a delayed post-test was administered at the end of the study. An analysis of the data, which included the pretest, instructional quizzes with four quizzes independently and then combined for an aggregate score for an immediate post-test, and the delayed post-test, yielded mixed results. The four instructional quizzes independently showed definition instruction to have the highest positive impact on student learning. In a measure of gains from pretest to instructional quizzes immediately after treatment, significant improvement in student learning was found only with word parts instruction. In a measure of performance from pretest to immediate post-test (aggregate score of instructional quizzes) there was a significant gain in students’ vocabulary competence, and from pretest to delayed post-test there was a significant decrement in students’ vocabulary competence. Age and language moderated vocabulary competence. Further tests of equivalency were mixed and should be interpreted cautiously, as there were a very small number of students in the group of 25 years or older and non-native English speakers.