Outlaw motorcycle gangs OMGs are an iconic element of the criminal landscape in the United States, the country of their origin. Members of OMGs may present to the emergency department ED as a result of motor vehicle accidents or interpersonal violence. When one member of an OMG is injured, other members and associates are likely to arrive in the ED to support the injured member. The objective of this manuscript is to discuss various aspects of the culture of OMGs so that ED personnel may better understand the mentality of the outlaw biker. Knowledge of their symbols, values, and hierarchy can be crucial to maintaining order in the ED when an injured outlaw biker presents to the ED. We used standard search engines to obtain reports from law enforcement agencies and studies in academic journals on OMGs. We present the observations of 1 author who has conducted ethnographic research on outlaw bikers since the s. The emergency department ED is at particularly high risk for violence against...