In order to improve library instruction and to produce data that shed light on the value of this core library service, the Hong Kong University of Science and Technology Library conducted a formal assessment on its instruction program in 2004. A group of 688 users from 25 one-shot sessions was surveyed by a questionnaire four to eight weeks after the sessions were conducted. Results showed that the majority of attendees remained positive about the usefulness of the library sessions; they retained and used the skills learned; the overall rating of the library sessions and the instructors were comparable to those of the university's credit course ratings.