Although persistent developmental stuttering is known to affect daily living, just how great the impact is remains unclear. Furthermore, little is known about the underlying mechanisms which lead to a diminished quality of life (QoL). The primary objective of this study is to explore to what extent QoL is impaired in adults who stutter (AWS). In addition, this study aims to identify determinants of QoL in AWS by testing relationships between stuttering severity, coping, functioning and QoL and by testing for differences in variable scores between two AWS subgroups: receiving therapy versus not receiving therapy. A total of 91 AWS filled in several questionnaires to assess their stuttering severity, daily functioning, coping style and QoL. The QoL instruments used were the Health Utility Index 3 (HUI3) and the EuroQoL EQ-5D and EQ-VAS. The results indicated that moderate to severe stuttering has a negative impact on overall quality of life; HUI3 derived QoL values varied from 0.91 (for mild stuttering) to 0.73 (for severe stuttering). The domains of functioning that were predominantly affected were the individual's "speech", "emotion", "cognition" and "pain" as measured by the HUI3 and "daily activities" and "anxiety/depression" as measured by the EQ-5D. AWS in the therapy group rated their stuttering as more severe and recorded more problems on the HUI3 speech domain than AWS in the non-therapy group. The EQ-VAS was the only instrument that showed a significant difference in overall QoL between groups. Finally, it was found that the relationship between stuttering severity and QoL was influenced by the individual's coping style (emotion-oriented and task-oriented). These findings highlight the need for further research into stuttering in relation to QoL, and for a broader perspective on the diagnosis and treatment of stuttering, which would take into consideration quality of life and its determinants. Learning outcomes: Readers will be able to: (1) Understand how the Wilson and Cleary (1995) model of quality of life could be applied to comprehensively assess the quality of life in adults who stutter, (2) describe how health related quality of life is impaired in adults who stutter, (3) mention affected domains of functioning that are related to health related quality of life impairment in adults who stutter, (4) describe the relationship between stuttering severity, functioning, coping and health related quality of life in adults who stutter, (5) describe differences in stuttering severity, coping style, functioning and health related quality of life between adults who stutter who have registered for therapy and adults who stutter who have not. (Contains 7 tables and 1 figure.)