The purpose of the study was to investigate : (1) the relationships between subjective life stress and mental health; (2) the relationships between the ability to be alone and mental health; (3) the relationships among subjective life stress, the ability to be alone and mental health; and (4) whether the ability to be alone buffers the effects of subjective life stress on mental health. The sample consisted of 818 students from five junior high schools (ages 13-15) in Taipei. Instruments used in this study included Life Stress Scale, General Health Scale, and the Ability to be Alone Scale. The main findings were as follows:

1. The subjective life stress was significantly related to mental health.

2. The ability to be alone was significantly related to mental health.

3. The subjective life stress and the ability to be alone were significantly related to mental health.

4. The ability to be alone showed a minor buffering effect in the relationship between subjective life stress

and mental health. The study indicated that the ability to be alone is related to mental health and the ability to be alone can moderate the impact of subjective life stress on mental health. The implications of this study for guidance of adolescence, education of parents, and future research were also discussed.