The authors studied paranoid ideation and obsession, using Derogatis' SCL-90, in the subjects of 2,564 male and 1,252 female college freshmen of Yeungnam University. The authors collected the reports of Self-Rating Paranoid ideation and Obsession Scale during the periods from January to February, 1987, and applied ANOVA and t-test on paranoid ideation and obsession scores in order to compare them between various psychosocial factors, and sexes. The results are as follows: 1. There was not significant difference in the mean averages of total paranoid ideation scores between male and female students: male students scored 4.16±3.09, female students scored 4.16±2.91. 2. High scored items were delusion and suspiciousness. 3. Fifty-nine male students (2.3%) showed high paranoid ideation scores of 12 or higher, while twenty-six female students (2.1%) showed the same scores. 4. There was strong tendency toward higher paranoid ideation scores in the students who were dissatisfied with their home atmosphere, college, department and familiarity of parents and those who had pessimistic view of self in the past, present or future in both group (respectively P<0.001). The male students who believed protestantism showed higher level of paranoid ideation scores (P<0.01). The male students who attended the department of fine art showed higher level of paranoid ideation scores (P<0.05). 5. There was significant difference in the mean averages of total obsession scores between male and female students (P<0.05): male students scored 10.40±5.43, female students scored 10.75±5.02 6. High scored items were perfectionism, indecisiveness, inattention & obsessive thoughts. 7. Thirty-eight male students (1.6%) showed high obsession scores of 25 or higher, while fifteen female students (1.2%) showed the same scores. 8. There was strong tendency toward higher obsession scores in the students who were dissatisfied with their home atmosphere, college, department and familiarity of parents and those who had pessimistic view of self in the past, present, or future in both group (respectively P<0.001). The female students who attended the department of home economic & whose educational fees were paid by her brothers & sister, showed higher level of obsession scores (respectively P<0.01).