Teachers and students in the English as a second language classes at the West New York (New Jersey) Adult Learning Center participated in a study to determine which patterns of classroom interaction and student characteristics were most highly related to the acquisition of oral proficiency in English. Differences in teaching styles and performances were related to the acquired proficiency of the students, who varied considerably in age, education, and previous experience with English. Teachers used a variety of instructional techniques; however, the audio-lingual and silent method were the principal techniques used. Student proficiency was measured at two points in time, and the intervening instruction was observed daily. Measures of speaking facility were either direct measures of proficiency, such as the Oral Proficiency Test developed for this project, or other measures of knowledge of English. Statistical analyses were used to relate differences in teacher behavior to gains in students' oral proficiency. Results indicated that teaching style did affect proficiency, particularly for certain types of students. This volume describes the research methodology, presents details of the statistical analyses, and summarizes the results. (Author/MV)