. Today, the addiction is considered as biological-psychological-social disease and numerous factors are effective in tendency to narcotics abuse.about individual factors, we can suggest the relationship between personality types and narcotics abuse.

The aim of present study is the investigation of relationship between personality types (introvert-extravert) and people's tendency to narcotics addiction.

In this study, statistical population is all of male- addicts in Babolsar city. Of these, 100 persons are selected as sample of study by sample random sampling from withdrawl addiction centers and camps in Babolsar city.

The results show that: it is significant relationship between people's high scores in both groups of personality types (introvert - extravert) and people's tendency to narcotics addiction so that, however people's scores are high in both groups of personality types (Introvert - extravert), to the same extent, there is probability of tendency to narcotics addiction.

Almost, in all of the studies about addiction, personality characteristics are as factors that cause person's addiction. Also, lack of development of personality is considered as an important factor. Among personality eminent characteristics, Introversion-extraversion can be as variable and important factor in tendency to narcotics addiction.