Background: Adolescence is an inevitable stage of mankind development that has paid attention because of its special sensation. Adolescence is an appropriate time to forming Identity (sense and concept of himself) that mix the individual's history and necessary capabilities for psychological health in adulthood. One of the serious dangers in this stage is adolescence tendency to the drug and substance abuse, and is one of the most prevalent disorders in youth and adolescence stage. The objective of this research is the survey on the relation between Identity styles and tendency to substance abuse among male medical university students.

Methods & Materials: This research is a sectional- type correlation study that has operated on the 339 persons of male, students that were educate in Alborz University of medical science. two standardized identification styles (ISI=G6) and questionnaire of recognizing risk exposed people, has used. Data collection operated by researcher in a stage and then data analyzed by using descriptive statistics (absolute and relative frequency and standard deviation) and inference statistics (χ2 test, regression) in SPSS 18 edition.

Results: The results that obtained from analyzing data show that 35.8 percent of students have informational Identity style, and 27.4 percent have normative style and 36.8 percent have Diffuse/ avoidant style. 47.3% of students have tendency toward substance abuse And also χ² test show that there is a significant relation between tendency to substance abuse and positive addiction history in family

Conclusion: There is a significant relation between Identity styles and tendency to substance abuse (P=0.001).