The purpose of this study is to explore a conceptual approach to assessment for one-shot library instruction. This study develops a new assessment instrument based on Carol Kuhlthau's information search process (ISP) model. The new instrument focuses on measuring and identifying changes in student readiness to do research along three dimensions--cognitive thoughts, affective feelings, and research actions--before and after the students receive one-shot library instruction at the beginning of their research. The development of the new instrument includes a validation process supported by statistical analyses. The results demonstrate that the students improved their research readiness after receiving one-shot library instruction. Contains notes.