This paper describes levels of processing in word production and how they may be impaired in acquired language disorders (aphasia). Specifically, it addresses how treatment of word retrieval impairments can inform not only our understanding of the disorders but also the underlying theories. This is illustrated using two examples. One example focuses on the use of different tasks in the treatment of word retrieval disorders, evaluating their efficacy and determining the nature of their effects. A second example uses the treatment of word retrieval disorders to address the contentious debate regarding whether homophones (e.g. pour/paw) share a single phonological representation, or have distinct representations for word production.