The purpose of this study was to examine the relationship between entering employment and mental health. A questionnaire was administered to 70 young women, before and after graduating junior college or university. Mental health and job satisfaction was measured. As a personality measurement, Cloninger's Temperament and Character Inventory was used. Results showed that low job satisfaction significantly worsened mental health after beginning to work. However, even when job satisfaction was low, mental health did not deteriorate if the person's reward dependence was high. The result indicated that reward dependent personality might have a buffering effect on mental health.