Objective: To estimate the prevalence of Japanese adolescents' alcohol use in Japan and the situations surrounding their drinking. Method: A general population self-administered questionnaire survey was conducted with a sample of 5,240 Japanese junior high school students obtained from 12 representative schools of the Chiba Prefecture in Japan. Results: Almost 80% of the boys and 75% of the girls reported having consumed an alcoholic beverage on at least one occasion. Consumption occurred most frequently on a ceremonial occasion (52.4%), followed by drinking with family (39.0%), with peers (20.6%), after a bath (9.7%) and at ritual parties among friends (9.3%). In this sample, a greater percentage of students in a higher grade reported a drinking occasion after a bath, at parties among friends, or with peers. However, this trend was not observed for drinking on ceremonial occasions or with family in the evening. A gender difference was observed for the prevalence of drinking after a bath. A majority of students agreed with the statement that minors' use of alcohol was 'acceptable depending on the situation.' This was in sharp contrast with their perception of cigarette smoking and solvent use (16.3% and 3.8%, respectively, endorsing the same statement). Conclusions: By sometime in their first year of junior high school (when most students are age 12 years), more than 75% of Japanese adolescents have tried alcohol. Prevalence rates and trends across grades are different depending on the occasions of drinking. The findings on situational drinking among adolescents of this age group appear to reflect that assimilation into Japanese drinking culture takes place early on in family or traditional settings.