In this article the development, utility, reliability, and validity of the Inventory for Deja vu Experiences Assessment (IDEA) are described. The IDEA is a 23-item self-administered questionnaire consisting of a general section of nine questions and a qualitative section of 14 questions. The latter questions comprise 48 topics. The questionnaire appeared to be a user-friendly instrument with satisfactory to good reliability and validity. The IDEA permits the study of quantitative and qualitative characteristics of deja vu experiences.