Introduction: Consuming alcohol mixed with energy drinks (AmED) has become a growing and popular trend among young adults worldwide. Although there have been some mixed findings, generally AmED use is associated with heavy drinking, risky behaviours and more negative outcomes, compared to alcohol use alone. Little research has been done outside of college samples and few researchers have investigated motivations for consuming AmED. Purpose: The purpose of the current research was to expand on previous research by investigating motivations for AmED use and the associations between AmED use and heavy drinking, alcohol use disorders, risky behaviours, and negative outcomes in community samples, while controlling for potentially important third variables, like sensation seeking. Methods: Using multivariate regression analyses the associations between AmED use and other variables were investigated in a randomly selected Canadian sample (n = 13,615) and a Canadian community young adult sample (n = 456). As well, an in-depth qualitative investigation of university students’ (n = 465) reported motivations for AmED and energy drink use was investigated using content analysis. Results: Compared to alcohol only, AmED use was found to be associated with heavy alcohol use, increased risk for alcohol use disorders, and increased risky behaviours and negative consequences (e.g., being a passenger in a vehicle with a drunk driver; drinking and driving; being involved in physical aggression; having harmful effects on relationships, health, employment) in both the Canadian and community samples. More frequent AmED use (e.g., weekly or more) was associated with ever having had a sexually transmitted infection. These relationships remained significant even after controlling for demographic variables and sensation seeking personality in the Canadian community sample. The most commonly reported motivations for AmED use were due to the taste of the beverage, enjoyment of a particular AmED (e.g., Jagerbomb), for increased stimulation (e.g., wakefulness, energy, alertness) while drinking, to facilitate “partying” or staying out late when drinking, to counteract the depressant effects of alcohol, for social purposes, and because of ease of availability (e.g., purchased by others/ given for free). Conclusions: This research has contributed to a better understanding of the relationships between AmED use and personality traits, drinking behaviours, and risk behaviours in two relatively large community samples. It has contributed to a better understanding of the motivations for AmED use and how these motivations may be related to heavy drinking and risky behaviours. Taken together, this research indicates that there may be something about AmED use which puts people at an increased risk of drinking heavily, engaging in risky behaviours, and experiencing harms, compared to alcohol use alone. Along with the accumulating research in this area, the current research could be valuable for directing and planning future research studies which are designed to investigate causative relationships and for formulating effective policies and intervention programs. / Graduate / 0621 / 0573 / kbrache@uvic.ca