Context: The importance of evidence from randomised trials is now widely recognised, although recruitment is often difficult. Qualitative research has shown promise in identifying the key barriers to recruitment, and interventions have been developed to reduce organisational difficulties and support clinicians undertaking recruitment. Objective: This article provides an introduction to qualitative research techniques and explains how this approach can be used to understand-and subsequently improverecruitment and informed consent within a range of clinical trials. Evidence acquisition: A literature search was performed using Medline, Embase, and CINAHL. All studies with qualitative research methods that focused on the recruitment activity of clinicians were included in the review. Evidence synthesis: The majority of studies reported that organisational difficulties and lack of time for clinical staff were key barriers to recruitment. However, a synthesis of qualitative studies highlighted the intellectual and emotional challenges that arise when combining research with clinical roles, particularly in relation to equipoise and patient eligibility. To support recruiters to become more comfortable with the design and principles of randomised controlled trials, interventions have been developed, including the QuinteT Recruitment Intervention, which comprises in-depth investigation of recruitment obstacles in real time, followed by implementation of tailored strategies to address these challenges as the trial proceeds. Conclusions: Qualitative research can provide important insights into the complexities of recruitment to trials and inform the development of interventions, and provide support and training initiatives as required. Investigators should consider implementing such methods in trials expected to be challenging or recruiting below target. Patient summary: Qualitative research is a term used to describe a range of methods that can be implemented to understand participants' perspectives and behaviours. Data are gathered from interviews, focus groups, or observations. In this review, we demonstrate how this approach can be used to understand-and improve-recruitment to clinical trials. Taken together, our review suggests that healthcare professionals can find recruiting to trials challenging and require support with this process.