Background: Supervised Injectable Opiate Treatment (IOT) is a complex, intensive treatment modality that has been effective in treating long-term, chronic, previously treatment refractory heroin users. The mechanisms that make it an effective treatment modality are little explored, and never in a UK context. Aims: In a UK supervised IOT context, this thesis set out to describe the long-term treatment trajectory of patients receiving IOT. Additional aims were to describe the experience of patients receiving IOT and ascertain the role of IOT in the patient’s overall journey of recovery. In so doing, the thesis contributes to the scientific understanding of IOT. Method: Quantitative measures are employed to describe treatment process and the effect of treatment duration on outcome. Qualitative measures are utilised to describe the following: patients’ drug use and treatment histories; goals for, motivations, and expectations of IOT; experience with IOT; satisfaction with IOT; views on the impact of IOT; and views of, and goals for, patients’ recovery. Results: Quantitative findings illustrate that some participants remained in IOT long-term, whereas others discharged or moved back on to oral treatment modalities. When long-term IOT was undertaken, initial gains made were sustained. Qualitative findings illustrate that patients conceive effective IOT as flexible, psychosocial, person-centred, and encompasses autonomous ongoing support. Recovery is perceived as an ongoing, individualised journey, and the need for support following both IOT and abstinence are identified. Discussion: Strengths and limitations of the research are discussed. IOT is best delivered as an individualised, time-limited, goal-driven, flexible treatment programme for those entrenched users with long-term, treatment refractory histories. Numerous findings have utility for policy and clinical practice and there is scope for examination of individually tailored treatment programmes through further research and, a systematic exploration of longitudinal outcomes.