Aims:To assess the impact of family and peers on both initiation and continuation of substance use among eighth, ninth and tenth grade adolescent high school students.Design:Population based cross-sectional study.Setting:Two high schools of West Bengal, India.Participants:416 students in class VIII, IX, and X in two schools.Interventions:None.Measurements:Substance use: initiation, sources, reasons for continuation. Then proportions and chi-square test was used for statistical analysis.Materials and Methods:This was a population based cross sectional study conducted among 416 students from class VII, IX and X in two high schools( urban and rural) of West Bengal, India selected by Multistage random sampling. A self administered anonymous pretested close ended questionnaire was used with the main outcome measures of initiation, sources, reasons for continuation of substance use based on WHO study team questionnaire.Results:Prevalence of substance use was found to be higher among the urban students (15.1%) than their rural counterparts (10.7%). The proportion of users was higher in the higher grades as compared to the lower grades. Among urban as well as rural students, 16 years and above were significantly more likely than their counterparts aged 15 years and below to report lifetime use. The mean age of initiation ranged from 12.6 to 13.9 years. Family members and friends were found to have a considerable influence not only on initiation but also important sources for money as well as the substance. Easy availability in the neighborhood was also an important correlate to continuation of substances.Conclusions:Family environment as well as peer groups has an important bearing on initiation and continuation of substance use. Experimentation of substance use motivated by peer groups is common among adolescents and starts early in life. Hence, it is necessary to provide health promotion programs directed toward students and their families which encourage attitude shaping among school children towards self-confidence and adequacy.