A study of English-as-a-Second-Language (ESL) learners' self-efficacy and its relationship to achievement is reported. Subjects were four students from the highest level reading and writing class in Indiana University's intensive English program. Each was interviewed in a tape-recorded session, to explore his/her English learning experience and perceptions of self-efficacy in English learning. The researcher also observed the participants' class five times after the interviews, examined writing assignments, and had them respond to two questionnaires, one asking direct questions about language skills and the other a standardized adult literacy and ESL learning self-efficacy questionnaire. Results for each subject are described separately, and conclusions are drawn from the group's results. It was found that the subjects' self-efficacy was generally significantly higher than their learning achievements. However, their achievements did correspond to their perceptions of their own ability. Participants' interest in class assignment topics and perceptions of the teacher's support also influenced self-efficacy, both negatively and positively. Required tasks and assignments were perceived as helpful in promoting persistence and aspiration. Additional factors found influencing self-efficacy included learner's performance, comparison with other learners, task complexity, and effort expended on a task. Contains 11 references. (MSE)