Background
Health-related behaviors developed in adolescence influence health later in life. Youth dietary behaviors, physical activities, mental wellbeing, and parent-child relationships are correlated with physical health, mental health and behavioral risk in their adulthood. In order to understand the prevalence of adolescent health behavior, relating factors, and to develop effective prevention strategies, the Taiwan Youth Health Survey (TYHS) was initiated in 2006. The survey was designed by referring to the Youth Risk Behavior Survey (YRBS), which was conducted every two years since 1990 by the US Centers for Disease Control and Prevention (US CDC) in the U.S., and Global School - Based Student Health Survey (GSHS), which was developed by the World Health Organization (WHO) in collaboration with United Nations' UNICEF, UNESCO, and UNAIDS; and with technical assistance from CDC.
The GSHS is a school-based cross-sectional survey and targets junior or senior high school student populations in Taiwan. The Health Promotion Administration collaborated with US CDC and launched Taiwan GSHS in 2013.This survey collects data on health behaviors and protective factors among students, such as family status, body weight, dietary behaviors, physical activity, hygiene, violence and unintentional injury, deviance behavior, mental health, health-risk behaviors, and sexual behaviors. The survey can establish trends in the prevalence of health behaviors and protective factors for use in evaluation of school health and youth health promotion
Since 2013, the survey was conducted annually on a national representative sample of students selected from the 22 counties/ cities in Taiwan.  Surveys only students in junior high schools and senior high schools are conducted every other year for collection of policy relevant informant develop priorities, establish programs, and advocate for resources for school health and youth health programs and policies.

Aim of the Survey
 To understand the prevalence of health risk behavior of the youth population.
 To understand the relation between background characteristics and health risk behaviors among the youth population.
 To investigate the co-occurrence of health risk behaviors among the youth population.
 To monitor trends in prevalence of health risk behavior of the youth.

Sampling Design
The sampling was designed by the CDC of the United States, following the protocol of the GSHS. In order to draw a national representative sample, the schools was categorized into 4 levels by the population density of its located township before sampling. The sampling method was a 2-step “probability proportional to size (PPS)”method, the sample schools was drawn first, and then sample classes in that school was drawn next. All students in the sample classes were invited to join the survey. The estimated sample size was about 6,000 students.

Survey Methods
The GSHS survey uses a self-administered, anonymous questionnaire to collect data. All staffs that administrate the GSHS survey has to attend a one-day training provided by the HPA. Three to six trained staff members from the local health bureaus are responsible to coordinate with the sample schools and decide the date and time of the survey in sample school. If local health bureaus are short of human resources, HPA would support and designate its staff. To avoid sample students from discussing with each other about the questionnaire, which might contaminate the data collected, all sample students in each sample school shall complete the survey one the same day at same school hour. The survey is conducted in the classroom of the sample classes. Informed consents are provided to parents of the sample students. The contents of the informed consent will make it clear the aim and the importance of the GSHS survey. The participation in the survey is voluntary, and the information is completely confidential. Both parents and the students have the right of refusal.