Since e-cigarettes were put on the market in 2007, the use of them has increased rapidly especially among young adults and adolescents. The purpose of this thesis was to identify young individuals’ harm perceptions of using e-cigarettes as compared to the harm perceptions of using carcinogens, and to compare the physiological effects of using e-cigarettes with those same carcinogens. Research was conducted by searching the Arizona State University Library website for articles that pertained to perceptions and physiological effects of e-cigarettes, conventional cigarettes, marijuana, and methamphetamine. Overall, young individuals have extremely low harm perceptions of using e-cigarettes, as compared to the other carcinogens. They perceived cigarettes to be the most dangerous and had the most knowledge on the subject, followed by methamphetamine, marijuana, and e-cigarettes with very little knowledge on the latter subjects. Many of the physiological effects of using e-cigarettes found in the research were shared with conventional cigarettes, marijuana, and methamphetamine. Specifically, using e-cigarettes results in negative physiological effects such as increased airway resistance, increased airway and lung tissue inflammation, increased bronchitic symptoms, increased mucin production, distal airspace enlargement, and increased cytokine and protease expression which are linked to COPD in chronic cigarette smokers. Other effects associated with decreased lung and respiratory function were shared with the chronic use of conventional cigarettes, marijuana, or methamphetamine. These findings can be used to inform young individuals of the harms that e-cigarettes may cause. More research needs to be conducted on the topic to identify the full range of physiological effects that using e-cigarettes may have on the body.