Background: Improving the quality and safety of patient care is at the core of everything that healthcare providers do. However, implementing sustainable improvements in practice is challenging, a problem that was experienced both in local practice and which is frequently acknowledged in the literature. This practicebased research study focuses on one of six dimensions of healthcare quality: efficiency and examines how it can be improved and sustained in the operating theatre setting in an academic teaching hospital. Aim: The aim of the study was to improve and sustain efficiency in operating theatres. The objectives were 1) to examine the impact of implementing interventions in practice to address the problem of delayed start times, and 2) identify the factors required to sustain improved outcomes. Methodology: A case study design was the research methodology used in this study. There were six case studies presented in this research. Five of the six studies focused on improving theatre start times and one study relates to implementing an anaesthetic preoperative assessment service. Both quantitative and qualitative data were used to measure performance data and guide changes in practice. A Quality Improvement methodology: The Model for Improvement was followed as a systematic approach to practically implement efficiency improvements. Results: Improved performance was achieved across all case studies which were carried out between six and 20 months. There were similarities between problems causing inefficiencies and interventions implemented with those presented in the literature as well as new findings that contribute to theory on theatre start time efficiency. Long-term sustainability of improvements was examined in five case studies between six and twelve-months post project completion using a sustainability framework by the Institute of Healthcare Improvement’s (IHI). Evidence of embedded practice changes and improved performance continued however inconsistent planning for implementation and sustainment of improved performance in the longer-term impacted on sustaining outcomes achieved in a sample of the studies.