Substance use is a worldwide problem and the prevalence is alarming, constituting an extremely significant public health problem, plaguing individuals and families and promoting major deterioration. Mental disorders resulting from substance use are very prevalent and can lead to severe conditions, even leading to the death of the individual. The results of this range from socioeconomic, physical, mental damage to death. Approximately 300 million people in the world use illegal substances, in an age group that circumscribes a population from 15 to 65 years old. The magnitude of the problem of drug misuse, seen in recent decades, has grown to such a serious extent that today it is a public health challenge. The International Day to Combat Drugs was established as a strategy to intensify the debate on the subject and to promote action plans in order to create preventive measures aimed at raising awareness among the population about the risk related to substance use and as a way to seek the decrease / eradication of this public health problem. About 1 in 200 people have problems with illegal substances, this alarming number tends to increase dramatically if measures are not intensified and if the population is not aware that substances kill. Text written by Psychiatrist Cláudia Muñoz of the CEFI Integration Team - Multiprofessional Treatment for Chemical Dependence.