This article examines assessment approaches and specific measures used by job-stress researchers to characterize aspects of work and the working environment (potential job stressors) and workers' reactions to these working conditions (strains). Self-report instruments, observational approaches, and physiological indicators are described. Problematic areas (e.g., the use of overlapping stressor and strain measures) and contemporary issues affecting job stress assessment (e.g., negative affectivity) are discussed. Recommendations regarding instrument selection and measurement improvements are offered. It is concluded that closer attention to measurement-related issues is critical to the advancement of knowledge in the field. Important needs include the identification and more frequent use of objective measures, the increased use of triangulation strategies, and a careful examination of the adequacy of existing constructs and measures for capturing the demands of contemporary work.