Background: Adolescence is a period of dynamic change representing the transition from rnchildhood to adulthood and is marked by emotional, physical, and sexual maturation. Habits rnthat are formed during adolescence had major effects in adulthood health and welfare ranges rnfrom 10-19 years and young people or youth is in the age ranges of 15 to 24 years old rnObjective: The aim of this study was to assess prevalence of premarital sexual initiation and rnassociated factors among Mersa Preparatory and High school students, North Wollo, Amhara rnNational Regional State, March 10-30, 2012. rnMethods: A school based quantitative cross sectional survey was conducted from March 10 to rn30, 2012. Stratified random sampling technique proportional to size was applied. Pretested, rnstructured and close ended questions prepared in English and translated to the local Amharic rnlanguage and self administered type of questionnaire was used. Data was entered using EPI rnINFO .version 3.5.1 and exported and analyzed using SPSS version 16.0 windows and multiple rnlogistic regression models were used to identify predictors of premarital sexual initiation. rnResults: A total of 356 respondents were involved in the study. The prevalence of premarital rnsex was 31.7%. The mean age of sexual initiation in the study population was 16.46 Â± 2.3 for rnmales, 16.6 Â± 1.4 for females and 16.5Â± 1.9 years for both sex. Being male by gender [COR 2.053 rn(1.278, 3.300) and AOR 1.703 (1.997, 2.910)], age greater than 15 years [COR 2.333 (1.075, rn5.063) and AOR 1.572(1.627, 3.941)], having pocket money [COR 0.446 (0.277, 0.720) and AOR rn2.102(1.244, 3.552)] were found to be significantly associated with premarital sex rnConclusion and recommendation: This study has revealed that early sexual initiation before rnmarriage was high and school adolescents started sexual intercourse very early and are rninvolved with high-risk sexual practices which were unplanned and unprotected. Consistent rnProvision of information about adolescent reproductive health in general and per-marital rnsexual practices and factors related to it in particular should be provided to the school rnadolescents by the concerned governmental and non-governmental bodies.