This project is concerned with figuring out under what conditions addiction serves as an excuse from blame. The first chapter argues that addicts have diminished control over their drug use. Chapter 2 develops the ethical framework that I will use to approach the question. Chapter 3 argues that addiction does not undermine moral responsibility. The upshot of this is that if addiction is excusing, it is not because addicts are the kinds of people who cannot serve as subjects for blame. Chapter 4 offers and defends a different account of addiction as an excuse, which holds that addiction is excusing for people with a certain kind of character and a certain kind of history. It also illustrates the practical application of my account and points to an important outstanding problem for future research.