The purpose of this research project was to study the relationship between drug consumption and sexual practices in teenagers in the city of Medellin, Colombia. A transversal studied was designed in order to identify the variables related to having had sexual intercourse under the effects of drugs or alcohol. The sample was made up of 955 teenagers between 14 and 17, who were in 9th, 10th and 11th grades in public and private schools in the city of Medellin. The results show that the prevalence of drug and alcohol influence in sexual intercourse is 43,67%. The most common drugs used for sexual practices are alcohol, marihuana, popper, cocaine and ecstasy. Consuming alcohol or drugs and having sexual practices shows an associated meaningful statistic (p= .001). The more common sexual practices under psychoactive substances are the exploratory ones (caresses and touching) (71%), vaginal penetration (63.67%), oral sex (45.30%) and masturbation (19.59%). Regarding the protection methods during sexual intercourse under drug or alcohol influence 55,9% always use a condom, 37,3% sometimes use it, and 6,8% never do it. This study proves what had been previously established by other research projects that show a high statistic association between drug consumption and sexual practices, but realizes that there is no statistically significant association between sexual practices under the influence of alcohol or drugs and the use or non-use of protective methods, which is the most important finding.