Introduction: Sexual risk behavior accounts for a large number of vulnerabilities for acquiring HIVrninfection. Alcohol use has been shown to increase high-risk sexual behavior. Moreover, the socialrndynamics that surround alcohol use, sexual risk behavior and HIV infection and interactions betweenrnthese issues warrant a search for alternative ways of dealing with the problem.rnWorldwide Human Immunodeficiency Virus poses an enormous challenge on the survival of humankind,rnand most serious infectious disease challenges to public health. Risk sexual behaviors among adolescentsrnand young adults have received growing attention during the past decade. Worldwide, 2.6 millionrnadolescents are newly infected every year, with sexual transmission being the most common way thernhuman immunodeficiency virus is contracted by adolescents.rnObjectives: To assess sexual risk behaviors, among preparatory and vocational students in Bishoftu cityrnadministration, Oromia Regional.rnMethods: Across sectional study was conducted from January to Jun, 2011 among preparatory andrnvocational students. Two stage sampling technique was used to select sample size of 924 students fromrnboth schools. Data were collected through anonymous structured questionnaire and pretested among otherrnstudents who were not participating in the study.rnThe questionnaire consists of socio-demographic characteristics, and sexual history of Preparatory andrnVocational students. After data collection the data were cleaned, audited and entered into EPI info andrnanalyzed using SPSS for windows computer software packages. A bivariate and logistic regressionrnanalysis was employed.rnResult: A total 875 students from Preparatory and Vocational schools completed the questionnairernmaking the response rate of 98%. Overall our study finding showed that 30.2% Preparatory andrnVocational school students were to be at risk sexual behavior. Risk sexual behavior was positivelyrnassociated with sex (being male) (AOR =1.47; 95 %; C I; 1.08, 2.02), age 18 years and above (AOR =rn2.62; 95% C I; 1.79, 3.83), drink alcohol frequently (AOR=1.93; 95% C I; 1.38, 2.68) and smokerncigarette frequently (AOR=168; 95% C I; 1.12, 2.52).rnConclusion and Recommendation: Considerable proportion of Preparatory and Vocational studentsrnwere to be at risk of sexual behavior. This study also found that age 18 years and above, male sex, drinkrnalcohol and smoking cigarette frequently was associated with risk sexual behavior. And more effectivernschool health program intervention should be implemented among school youths to prevent risk sexualrnbehavior through school based sex education. Intervention strategies among school youths should bernimplemented to prevent substance use (alcohol and cigarette) by the use of health- promoting schoolrnmodel charter of WHO.