The purpose of this study was to identify the factors that significantly influence the attitudes and perceptions of high school health education teachers relative to HIV prevention instruction. Despite a steady decrease in the number of diagnosed cases each year, HIV/AIDS continues to rank as one of the leading causes of illness and death in the United States. Individuals between the ages of 13 and 19 years are particularly vulnerable for HIV transmission, as evidenced by the steady increase in the number of reported infections in this age group over the past decade. Underlying this trend is a growing lack of awareness, a decreasing perception of vulnerability and a general lack of accurate knowledge regarding HIV/AIDS among adolescents and young adults in the United States. The CDC, along with a number of researchers in sexuality education, recommends that education about HIV prevention is most appropriate and effective when executed within the context of a comprehensive school health education program that establishes a foundation for understanding the relationships between personal behavior and health. While the CDC's 2006 School Health Policies and Practices study indicates that 31 states require instruction in HIV prevention, research indicates that there is great variability between states and individual districts in the provision of the requirements for the certification, licensure, and training in sexuality education of the teachers providing that instruction. The population of interest in this study was high school health education teachers in public school systems in the United States. A systematic random sample of 800 high school health education teachers representing states with mandates requiring instruction in HIV prevention and states with no such requirements was selected from a list of public high schools derived from the Common Core of Data (CCD) of the United States Department of Education's National Center for Educational Statistics database. An a priori power analysis, for external validity of the results, suggested a sample size of 374 completed surveys based on a 5% sampling error and 50/50 split in responses for a population of 11,250 schools. Sample size was determined based on alpha at .05, the effect size at .20 and 90% power. Based on response rates of studies with similar populations, a total of 800 surveys were sent to lead health education teachers in the selected high schools. Seventy-nine surveys were undeliverable, leaving a potential sample size of 721. A total of 362 high school health education teachers (50%) responded. While there is almost complete agreement (99%) among respondents in this study that HIV prevention instruction is needed, the results of this study indicate that there is significant variance in outcome expectations, efficacy expectations, perceived barriers and benefits, and attitudes of high school health education teachers about teaching HIV prevention. The factors in this study that emerged as most significantly influencing the attitudes and perceptions of high school health education teachers about teaching HIV prevention were related primarily to teacher preparation and training and the number of years of experience teachers had teaching health education. The presence of a state mandate requiring HIV prevention instruction was significantly associated with higher efficacy expectations and more perceived benefits by high school health education teachers, but did not appear to have significant influence in relation to practices in the classroom. Characteristics of high school health education teachers that were significantly related to attitudes, perceptions and instructional practices included the age, gender and race/ethnicity of the instructor. The findings of this study are consistent with and affirm findings from previous studies that have emphasized the significance of teacher preparation and training relative to teachers' perceptions, attitudes, perceived benefits and barriers, and efficacy and outcome expectations, which ultimately influence student outcomes. Findings from this study also indicate the need to further investigate certain teacher characteristics, such as race/ethnicity, age, experience level, and gender to determine the extent that those variables may influence curricular content and instruction.