The purpose of this study was to examine the effects of moderators on the stress of job loss and mental health. Participants were 357 subjects from a list of unemployed persons supplied by a local (Suwon City area) labor agency. Their psycho-social characteristics, demographic variables, and levels of mental health were measured by means of a set of questionnaires. Psycho-social characteristics included optimism, social support, and self-esteem. Sex, age, education, number of family members, marrage status, religion, and previous jobs were utilized as demographic measures. To measure mental health, SCL-90-R was adopted. Results show that 1) demographic characteristics do not moderate the effects of job loss stress on mental health; 2) psycho-social variables, especially optimism and self-esteem, are powerful moderators on job loss stress and mental health; and 3) social support. which has generally been treated as a representative moderator in stress research, does not function at all as a moderator,. The implications of these findings are discussed.