BACKGROUND: With the persistent increase of all kinds of illegitimacy and crime, researches on the reasons that induce the occurrence of illegitimacy and crime become relative important issues at present, while the personality and socio-psychological factors of the offenders are also reasons cannot be ignored.OBJECTIVE: To investigate the personality and mental health situations of male prisoners to promptly correct the bad personality and mentality of the prisoners.DESIGN: An observatory comparative survey based on prisoner as subjects and normal individuals as controls.SETTING: Department of psychology in a medical college hospital.PARTICIPANTS: Totally 575 male prisoners were selected from the First Prison of Guizhou Province between December 2001 and March 2002 into study group. And 265 peasants and workers of Yunguan Township, Guiyang City were selected during same period into control group. All controls were male with matched age and education background to that of the study group.METHODS: Eysenck's personality questionnair(EPQ) and symptoms checklist 90(SCL-90) were used to asses the subjects and controls of both groups and the results were compared between two groups.MAIN OUTCOME MEASURES: Comparison of EPQ and SCL-90 scores between two groups.RESULTS: Extroversion, nervosity and psychosis scores in EPQ were significantly higher in study group(9.97±2.32, 12.00±2.62, 11.04±2.44) than control group(9.28±2.77, 10.25±2.68, 8.03±2.51)( P ＜ 0.01 ), while the score of conceal in EPQ was slightly higher in study group than control group ( P ＞ 0.05) . Positive numbers of study group in each dimension and each type of EPQ were significantly higher or lower than that of control group ( t = 2. 05-3.06, P ＜ 0.01 ). Total score, total mean,number of positive items and scores for 9 factors in SCL-90 were significantly higher in study group than control group( t = 3.23-7.89, P ＜ 0.01 ).CONCLUSION: Compared with ordinary adults, male prisoners have significant extroversion personality, unstable emotion, psychosis inclination and serious mental problems, which suggests the bad personality and mentality of the prisoners should be corrected simultaneously when they receive reformations.