The phenomenon knows as “maras” (literally “groups”, but to be read as “gangs”) isn’t really a new one: it originated in Los Angeles, U.S.A., in the 1980s. It was a form of self-defence Salvadoran immigrants thought of, in order to protect themselves from better rooted and more powerful Mexican gangs. With the years, it developed into a proper organised criminal group, with codes, hierarchies and many distinctive, highly symbolic traits (the most notable ones being specific tattoos and extreme violence). Nowadays, affiliation has widely extended to Hondurans, Guatemalans, and Nicaraguans. Their activities usually include drug smuggling and sales, arms trafficking, auto theft, carjacking, home invasion, assault, aggravated assault, assault on law enforcement officials, drive-by shootings, contract killing, and murder. Although there are traces of the gangs in other countries, such as South America, Canada, and more recently sporadically in Europe, they operate mainly in the U.S. and Central America. In fact, the bridge between the two has become so strong and organised, it is rather impossible to control. This research project focusses on the development of the initial phenomenon into an organised criminal group, defining the causes and identifying its characteristics. Nowadays, the reasons behind the groups’ activities have substantially parted from the original protective schemes. Acknowledging this, the study argues that the code and motivation behind that extremely violent behaviour still remains unaltered. The explanation has to be sought in the changed composition of the maras, the exacerbated relation with society (rival gangs and law enforcement included), both in the U.S. as well as in Central America.