The purpose of this survey research was to study the knowledge, attitude and preventive behavior toward AIDS among male students and male workers, and to study the relationships among knowleged, attitude and preventive behavior toware AIDS, in-cluding the relationships among various factors (e.g. age, education, economics status, marital status, unrestricted life-style and place of work), which may correlated with knowledge, attitude, and the behavior on prevention of AIDS infection. The sample consisted of 360 male workers and 360 male students, who were in Roi-et prevince, age 14-21 years. Results: In male worker group : a majority of the sample ha knowledged about AIDS in low level 54.2% (...=14.52, SD=3.45). Attitude toward AIDS in the middle level 59.72% (...=39.21,SD=3.56),and preventive behavior in low level 54.44% (...=8.59,SD=2.44). The analysis of the relationships among knowledge, attitude and preventive behavior on AIDS indicated that they were correlated. The knowlegde about AIDS significantly related to education, economic status, unrestricted lifestyle and place of work. Attitude significantly related to education and unres-tricted lifestyle. Preventive behavior toward AIDS related to age, education, economics status, marital status, place of work, but was not related to unrestricted lifestyle. In male student group : knowlege about AIDS was rela-tively good 72.50% (...=16.54, SD=3.05), Attitude toward AIDS was in the medium level 59.72% (...=40.33, SD=3.60). The majority of this group has positive preventive behabior on AIDS.(77.50%) It was found that there were relationships between knowledge and attitude, but knowledge, attitude were not related to preventive behavior toware AIDS. AIDS preventive behavior significantly related to the factors: age, education, economics status, unrestricted lifestyle, but knowledge about AIDS was not related to all these factors. The research finding indicated that the sampled population had knowledged about AIDS and preventive behavior at low level. It is suggested that the health officers ought to have health education concerning AIDS, and should be a continuing process. But this activity needs cooperations from employers of those workes. However the health educational program should distribute information to the other risk group and all people in