The aim of this study is to evaluate the impact of long-term occupational exposure to elemental mercury vapor (Hg°) on the personality traits of ex-mercury miners. The study groups included 53 ex-mercury miners previously exposed to Hg° and 53 age-matched controls. Their previous occupational exposure, as well as some biological indices of actual non-occupational exposure, were evaluated. Miners and controls completed the self-reporting Eysenck Personality Questionnaire (EPQ) and the Emotional States Questionnaire (ESQ). Group differences were analyzed through the application of ANOVA software. The relationship between the indices of previous occupational exposure and the observed personality traits was evaluated by machine learning methods (regression trees). The mercury miners were intermittently exposed to Hg° in intervals – cycles for a period of 7-31 years at air Hg° concentrations ranging from 0.14 to 0.45 mg/m3. The miners' mean cycle urine mercury (U-Hg) level (range 20–120 μg/L) and cumulative U-Hg level (range 1286–21390 μg/L) were very high. The present non-occupational exposure to mercury was very low in both groups. The low extraversion and lie scores shown by EPQ suggest that miners are more introverted and sincere. The results obtained from ESQ indicate that mercury miners tend to be more depressive, more rigid in expressing their emotions (indifference), and are likely to have more negative self-concepts than the controls. The tendency towards emotional rigidity, negative self-concept, and partly also introversion seems to be associated with some biological indices of occupational Hg° exposure, but not the lower score of lie found in miners. Higher occupational Hg° exposure (cycles U-Hg level > 38.7 mg/L) in interaction with moderate alcohol consumption (<26 ml/day) seems to have had a decisive influence on the development of miners' depression. Despite the limitations, long-term intermittent, substantial exposure to Hg° in interaction with alcohol remains a plausible explanation for depression, disposition to emotional rigidity, and negative self-concept found in mercury miners in the period after exposure.