OBJECTIVES: Perceived availability is commonly associated with adolescent alcohol use. Little is known about the factors which shape this perceived availability. The present study investigates (1) whether perceived alcohol availability is related to the characteristics of the adolescents' social environment and the per capita outlet density in the community and (2) whether adolescent alcohol use is related to perceived availability, social environment characteristics and outlet density. METHODS: Multilevel structural equation models were estimated based on data from a national representative sample of 6183 adolescents in the 8th and 9th grades of school (mean age 14.8 years) in 254 communities in Switzerland. FINDINGS: Social environment characteristics, that is, having peers and siblings who drink, going out without parental knowledge of the adolescents' whereabouts, drinking in public settings and the density of on-premises but not off-premises alcohol outlets, were related to perceived availability. Adolescent alcohol use increased with the permissiveness of social environment characteristics and with increasing perceived availability. Community-level perceived availability and the density of on-premises but not off-premises outlets were related to volume drinking but not to the frequency of risky drinking occasions. CONCLUSIONS: Perceived availability and drinking volume appear to be shaped by the adolescents' social and physical environments. Adolescents who have a variety of opportunities to obtain alcohol might develop the impression that underage drinking is common and socially endorsed. Consequently, preventive actions to curb adolescent alcohol consumption should take into account the social acceptance of drinking and the physical availability of alcohol in the community.