This paper focuses on the nature of job insecurity and addresses conceptual as well as methodological issues affecting our understanding of its consequences. A review of the literature suggests that a great deal of theoretical and empirical work is needed to capture the nature of job insecurity, develop psychometrically sound measures of the different aspects, and arrive at valid conclusions regarding the effects of insecurity. First, job insecurity is defined as a subjectively experienced stressor which may be divided into different dimensions. Second, the multiple aspects of job insecurity may have divergent consequences or at least be differentially related to potential outcomes such as work-related attitudes, job performance, physical health, mental well-being, and job-induced stress symptoms. Third, given that most studies on job insecurity have been cross-sectional, a lot of work remains before we know how, or if, insecurity contributes to changes in such outcomes. Fourth, there are a number of plausible factors that may moderate the relationships between job insecurity and its potential outcomes. Addressing these issues in theoretical as well as empirical work is necessary, we argue, to improve the understanding of both what job insecurity is and what it may imply for the individual.