In general both animal and human studies indicate that there is indeed an association between noradrenergic functioning and the expression of aggression. However, it is apparent that the details of this connection are unclear. Overall, the review implicates the noradrenergic system in expressions of aggression in animals and humans. Nonetheless, since many other systems are involved, it might be useful to conduct more research utilizing human participants. A substantial body of research exists concerning the neurochemistry of aggressive behavior. In order to fully understand any behavior, it is important that research evaluate the interactions among these various causes. The objective of this article is to review evidence regarding norepinephrine’s influence (i.e., the noradrenergic system) on aggressive behaviors. Norepinephrine plays a critical role in an organism’s ability to process sensory information and environmental stimuli. It also contributes to a variety of attention and arousal-related processes and has been implicated in the development of attention-deficit hyperactivity disorder (ADHD), sleep and arousal disorders, panic disorder, and post-traumatic stress disorder. In order to fully comprehend the role that norepinephrine plays in the expression of aggressive behavior, two research questions are addressed: (1) is there a connection between norepinephrine and aggressive behaviors and if yes, (2) what is the nature of the norepinephrine, aggressive behavior relationship? The article reviews animal and human research pertaining to each of these questions. Tables, references