Most studies on the relationship between job insecurity and well-being have focused on the effects of employees' overall concerns about the continued existence of the job as such (quantitative job insecurity). Comparatively little research has examined perceived threats to valued job features (qualitative job insecurity). The overall aim of this study was to investigate the relative strength of associations of quantitative and qualitative job insecurity with job-related (job satisfaction and burnout) and general (psychological distress and psychosomatic complaints) well-being, and health-related behavior (absenteeism and medical consultation). Controlling for sociodemographics, negative affectivity, and job characteristics, these relationships were tested in a sample of 7,146 Belgian employees in the banking sector. The results suggest that both quantitative and qualitative job insecurity are important stressors.