Anke C Winter, Graham A Colditz Division of Public Health Sciences, Department of Surgery, Washington University School of Medicine, St Louis, MO, USA Abstract: Clinical trials are one of the key study designs in the evolving field of comparative effectiveness research. Evaluating the effectiveness of interventions in real-world settings is complex and demands a rethinking of the traditional clinical trial approach as well as transformation of the clinical trial landscape. Novel strategies and refinement of existing approaches have been proposed to generate evidence that can guide health care stakeholders in their decision process. The purpose of this review is to discuss clinical trial design approaches in the era of comparative effectiveness research. We will focus on aspects relevant to the type of clinical trial, study population and recruitment, randomization process, outcome measures, and data collection. Keywords: review, clinical trial, comparative effectiveness research