Work conditions characterized by uncertainty and ambiguity are potential stressors for employees. One such stressor is job insecurity. This longitudinal study of 207 automobile manufacturing workers indicates that chronic job insecurity is predictive of changes over time in both job satisfaction and physical symptoms. Extended periods of job insecurity decrease job satisfaction and increase physical symptomatology, over and above the effects of job insecurity at any single point in time. These results indicate that job insecurity acts as a chronic stressor whose effects become more potent as the time of exposure increases. Worksite health professionals should develop strategies for reducing the impact of job insecurity on employee well-being, particularly in industries where employment opportunities are declining.