Violence is widely associated with organised crime, specifically drug markets, and is one of the features that differentiates illegal capitalism from legitimate business. This thesis is informed by a series of ethnographic interviews and informal conversations with former drug market participants and examines the causes of business related violence Dublin’s illegal drug trade. The research also investigates the interpersonal dynamics of violence amongst actors and provides insight into the characterological traits of violent people. The thesis begins with an examination of the role of violence amongst addicts in the street retail market and situates violent acts in the context of a compulsive disorder that suppresses moral standards and diminishes sympathy with victims. The relationship between profit oriented dealers and their often addicted customers is analysed to understand the intricacies of debt enforcement in the drug trade, and the thesis offers an explanation of dealers violence that is, at least in part, a response to the credit based system of commerce that the trade depends on. Paranoia is rampant amongst actors in the drug trade and they often suspect betrayal from within their own circle of friends and associates. Further, many of these men have a great sense of self-regard and are highly sensitive to the humiliation of personal insult. The research also looks at the violent practice of the more powerful actors in the illegal drug trade; the dominant criminals who maintain their positions for many years and accumulate great wealth. Many of these men suffer as a result of their way of life and can experience deterioration of their psychological health and emotional wellbeing as a result of living with the intense pressure of interpersonal conflict. Desistance from crime is possible for some of the men who have been very violent in the pursuit of profit and power.