Background: Performance-Enhancing Drugs (PEDs) are used by young adults to enhance physical performance and appearance. There are many medical problems associated with Performance-Enhancing Drugs. Aim of the work: this study aimed to estimate knowledge, attitudes and practices about the hazards of PEDs among young adults (18-28 years old) in Qassim University. Method: this was a descriptive cross-sectional analytical study carried out among male students at Qassim University, Kingdom of Saudi Arabia during 2014-2015. A self-administered questionnaire was completed from 134 male students in three colleges, one medical and two non-medicals. Results: prevalence of use in the medical students were 66.7 who were previously used AS and the half (33.3%) in non-medical students, but the current use among medical student was 16.7%, less than non-medical (83.3%). Regarding the source of using PEDs , the highest percentage in the medical students from friends, and the doctors in non-medical students. The prevalence of knowledge of medical students who know about side effect of using PEDs was 62,1 % more than non-medical (37,9 %). The majority of medical student recognized liver disease (61,9%), infertility (60%), gynecomastia (65%), shrinking testicle (62.5%) and hormonal disturbance (37.1%) compared to non-medical who knew about liver disease (38.1%), infertility (40%), gynecomastia (35%), shrinking testicle (37,5%) and hormonal disturbance(26,9%). Medical students showed positive attitude towards the use of PEDs (31.8%) which showed less than non-medical students (68.2%). As (61.1%) of non-medical believed the PEDs were responsible for improvement their performance conversely, 38.9% of medical students believed in that improvement. Conclusion, the non-medical students knew about the benefits of using PEDs for performance enhancement (47%) more than medical students (24%), thus non-medical students believed of enhancing their performance by PEDs more than the medical students. The medical and nonmedical students who used PEDs had exposed to their side effects therefore, we should pay more attention to educate those about them more.