The study of attitude and health behavior of Chiang Mai University students aimed to find the direction to decrease risk factors in health behavior. 4, 497 of 18, 489 undergraduate students, surveyed by Stratified Random Sampling, were analyzed in difference method that influence to attitude and health behavior by using Descriptive Statistics, Category Principal Component Analysis, Canonical Correlation, Category Regression, Nonparametrics and Analysis of Variance. Using the Category Principal Component Analysis, the factors that influence to attitude and health behavior are the faculty of students, the academic year, sex and level of physical condition. At.05 level of significance, the correlation of fundamental information, attitude and health behavior of each faculty is 0.894. The faculty of students is influenced to medical history, smoking, sexual behavior in the past 6 months and drinking alcohol. Relationship between risky behaviors are drinking alcohol, drinking alcohol before riding a motorcycle, drinking alcohol about 1 hour before driving a car, smoking and having sexual intercourse in the last 6 months and they related to expenditure pattern. The majority causes of risk behavior in risk group are sex, academic that students began to study, income and expense. Risk behavior in each faculty are different. The most risky behavior if ranged with the number of students of each faculty answering the question were wearing helmet, never having health check up in the last 1 year, using safety belt while driving a car and smoking, respectively.