Abstract Repertory Grid Technique (RGT) derives from Personal Construct Psychology. The technique aims to understand how participants view objects, events, or people chosen as a kind of thematic sample by comparing them against each other, revealing the participant’s constructs. After introducing the “fundamental postulate” and corollaries developed by its founder, George Kelly, the chapter explores how this technique may be applied in the field of SLA or language education. After discussing how this highly adaptable technique has been used, the chapter shows how researchers can gain qualitative and quantitative data on research questions relating to change over time or how different members of a group perceive a phenomenon. Although this technique presents some challenges for generalization, the chapter concludes by showing how data may be analyzed and used productively.