The need for effective programs to delay sexual activity and to educate adolescents regarding the human immunodeficiency virus (HIV) has never been greater. Statistics point out that a significant number of teenagers throughout the United States engage in behavior that increases their risks of becoming infected with HIV. This study examined adolescents' Acquired Immune Deficiency Syndrome (AIDS)-related knowledge, beliefs, and practices by age, sex, age and race/ethnicity; assessed the levels of students' high risk behaviors; and assessed the changes in school based AIDS education programs and policies. Maryland high school students were surveyed in 1988 and 1989. The 1988 study sample consisted of 817 students; the 1989 sample consisted of 5,459 students. The results clearly showed that the majority of students had a realistic perception of their susceptibility to the disease. Most of the students surveyed indicated a correct knowledge of the modes of HIV transmission, modes of preventing AIDS infection, and current facts about AIDS. Their attitudes about AIDS education were very positive. During the second year of the survey, increases in correct responses were found in all major areas of concern. Their level of knowledge did not vary significantly by either sex or race/ethnicity. However, there appeared to be a gradual increase in knowledge, specifically in the area of sex education from the age of 13 to 18. (ABL)