Self-medication is a common event. To use drugs correctly, a basic knowledge about drugs is required. Poor data are available about adults' drug knowledge. Furthermore, adolescents' basic drug knowledge has not been investigated. This study was designed in order to explore adolescents' drug use and knowledge and the factors that influence them. A total of 56 tenth grade students between 15-17 years of age at a secondary school in Dresden, Germany were enrolled in a pilot study by answering a self-completion questionnaire. Of adolescents, 57% took from one to six different drugs in the 2 weeks before questioning. In particular, a chronic consumption of non-opioid analgesics was found. Some 15% of adolescents took headache remedies at least several times per month. Self-acquisition occurred more often for these drugs than for any other drug group. The best score for drug knowledge was 10 out of 13 possible points and only 43% of students attained from 7 to 10 points. Astonishingly, more than two-thirds of adolescents could not describe in their own words how a medicinal agent is ingested. Female gender and a chronic drug consumption were detected as influencing factors of better drug knowledge.The results indicate that adolescents gain drug knowledge through drug consumption and not before taking drugs. This leads to a potential risk particularly in the case of self-medication.