Introduction: Three basic strategies against substance abuse are control of distribution, treatment of dependents and prevention. Recent years experiences have shown the significant importance of prevention. Considering the decrease in age of substance abuse onset, parents’ knowledge about this phenomenon and consequently its early prevention and control in the family is very important. Method: In this cross-sectional study performed in 2005, knowledge of 600 parents of Kerman highs schools’ and secondary schools’ students in relation to the symptoms of substance abuse was determined by using a researcher-made questionnaire. Results: In whole, 20.1% of the participants had high school or higher educational level and 11.7% of them had history of substance abuse in their family members. The highest knowledge scores in physical symptoms belonged respectively to alcohol (23%), opium (17%) and cigarette (15%). In relation to psychological symptoms, the highest scores were obtained for tranquilizers and analgesics (29%) and then cigarette, alcohol and opium (24%, 19% and 17% respectively). Conclusion: Insufficient Knowledge scores, especially in regard to substances with increasing rate of use is a serious warning requiring serious attempts for increasing knowledge of all classes of society especially parents. This should be done continuously and by using the most efficient educational programs and cooperation of all related organizations