The purpose of the study is to identify the differences about knowledge and attitude between the subjects exposed to pc pornography and the control group not exposed to pc pornography. The study was executed from July 12 through July 16. The subjects were 423 middle school boys. The comparison points were their ethical sexual knowledges and sexual attitudes. The collected data was analysed by SPSS WIN(including multiplicand, percentage, x2-test, revised Fisher and t-test). The results of their study were as follows ; 1. The pc-related characteristics of the subjects. The subjects exposed pc pornography showed 51.8% rate of exposure to printed pornography. The control group showed the rate of 26.4%. The former group owned their pc(81.5%), however, the latter group showed 66.7%. The former group set their pc sets in their study rooms(66.1%) however, the latter group installed those in their study rooms(73.6%). The former group experienced internet pc communications(62.5%),however, the latter group showed 40.2%. The former group made use of their pc sets in recreation(entertainment) programs(77.0%), however, the latter group showed the rate of 67.8%. The former group showed that their school performance levelled up after their pc manipulation(80.0%), however, the latter group showed the rate of 86.2%. The former group replied that their pc manipulation contributed to their friendship(50.3%), however, the latter group showed the higher rate of 74.7%. The both groups replied that their family dialogs and contacts rather reduced (78.9% and 78.2% respectively). The both groups revealed that they reduced the TV watching the rate 76.5% and 48.3% respectively. The differences between two groups were surveyed in the level of 95% significance and the items such as "contacts to printed pornography, pc possession or none, pc use rate, friendship occasions and the reduced time of TV watching" showed the significant differences. 2. The differences of two groups' sexual knowledges. As to the sexual knowledges, the both groups showed 41.1 and 34.1 points against 100 points respectively. The statistical differences were significant(t=2.72, p=.007). The 5 items among 17 showed the significant differences between two groups. "The concept of masturbation" was x2=5.033, p=.025. "The prejudice to masturbation" showed x2=9.902, p=.002 "The difference between female and male as to sexual excitement" showed x2=7.985, p=.005. "The positiveness of masturbation" showed x2=10.205, p=.001. "The differences between two sexes as to sexual impulse and sexual desire" showed x2 =8.463, p=.004. In conclusion, The former group showed the higher knowledges than the latter group. 3. The differences of two groups' sexual attitudes. The 4 items such as "the curiosity to the other sex"(t=2.22, p=.027), "the attention to pornography"(t=3.39, p=.001), "the permission to pre-marriage intercourse"(t=2.15, p=.032) and "the preference to the female body exposure"(t=2.67, p=.008) showed the differences between two groups as to sexual attitudes.