The purpose of this study is to examine the realities of knowledge and attitude about smoking among high school students, to analyze the relation among knowledge of smoking attitude about smoking, and smoking behavior. For the data, 1,522 boys" high school students living in Pusan were selected. The data were analyzed with the SPSS PC+ statistical package using t-test, multiple regression and path analysis. The main results are as follows; First, smoking group has lower knowledge of smoking than non-smoking group. Second, smoking group has more positive attitude about smoking than non-smoking group. Third among the demographic variables pecket money, scholastic attainments, grade, SES, and religion influence on smoking behavior directly and indirectly. Fourth, among the smoking environmental variables parents" smoking, sibling"s smoking. the number of smoking family. close friends" smoking, the number of smoking friends, family"s thought about smoking, knowledge of smoking attitude about smoking influence on smoking behavior directly and indirectly.