Pattern of Substance Use in High School Students: A High School Study in Ubonratchathani.The objective of this research is to study pattern of substance use in high school students; including alcohol, cigarette, and amphetamine especially. The factors associate to such behavior, progression of use, consequence, and management of substance use problem from the school were explored. The methodology of the study was a qualitative research. The study site was a high school in Ubonratchathani province, by purposive selection. Key-informants were the students who had experience in substance use or exposed to the user, and the teachers who were advisor of students. Data collection was done from August 1999 to February 2000, by in-depth interview (student 10 cases) and focus group discussion (teachers, 2 groups/18 cases). Then, the data was analyzed by content analysis method.	For the key-informants, the student group, the substance use began from alcohol drinking and then cigarette smoking in a short period of time, between grade 7-9. The use of amphetamine came later, depend on the exposure opportunity to the user and participation with the user group. The pattern of use was similar in each key-informant; initiate from group participation, expose to peer or sibling whom experienced of use, and then ask to try or encouraged by peers. Continue of use was follow because of pleasure and group participation. The significant factor associated with substance use, especially amphetamine use, was their own while the others were influence indirectly; such as social and school environment, family role and status, group participation, and availability of substance. And the factors associated with lowering of use or abstinence were intention of themselves and/or peer group to quit, avoidance from the user group, difficulty in drug seeking, less of money, appearance of the police in school and urinary testing for substance use. These factors influenced frequency of use by the time. However, among high school users, recreational or occasional use with regular use at times were the majority of them.	Among the user, it was no significant impact while taking alcohol and/or cigarette. But in case of amphetamine, there were both behavioral and physical changes when the frequent of use was increase. Behavioral changes might be delinquent or problem behaviors in school, alter school performance, use much more money, and lie their parents. From their viewpoint, physical changes were transient and no significant to worry about it. And no psychiatric sign and symptom or disorder was appearing. In opinion of student group, although alcohol drinking or cigarette smoking seems to be a part of adolescent life, but amphetamine use was only individual behavior.	When the situation about substance use in high school to be asked, the key-informants said that alcohol drinking and cigarette smoking initiated in grade 8, amphetamine use by smoking appeared in grade 9, the user rate increased in all type of substances between grade 10 and 11, and then decreased in grade 12. The favorite substances in boys were alcohol, cigarette, and amphetamine; while in girls were alcohol, amphetamine, and cigarette respectively. And evidence of inhalant or glue was not found in last 1-2 years.	About programs against substance use problem in school such as campaign or education, there were not interested and less participation from the user group and not influence their substance use behavior. In addition, it was no other action plan or relevance program from the school while the policy and strategy were not clear defined.