The introduction and a theoretical summary of language anxiety research (Chapter 1) are followed by four chapters: Chapter 2 presents a meta-analysis of the widely used Foreign Language Classroom Anxiety Scale's (Horwitz, et al., 1986) factorial structure; Chapter 3 reports on a validation study of the Hungarian version of MacIntyre and Gardner's (1994) Input, Process, and Output Anxiety Scales; Chapter 4 presents the development of a skills-based anxiety questionnaire through a three-phased study consisting of an exploratory qualitative phase as well as two quantitative phases using Rasch analysis; and Chapter 5 focuses on empirical approaches available for tapping into the dynamic change of this emotion, including the idiodynamic method and quantitative analyses such as latent growth curve modeling and dynamic cluster analysis.