BACKGROUND.Providers play a vital role in the successful recruitment of underrepresented patients to cancer clinical trials because they often introduce the opportunity of clinical trials. The purpose of the current systematic review was to describe provider‐related factors influencing recruitment of underrepresented populations to cancer clinical trials.METHODS.To find original studies on the recruitment of underrepresented populations to cancer clinical trials, electronic databases from January 1966 to December 2005 were searched; hand‐searched titles in 34 journals from January 2003 to January 2006; and reference lists were examined of eligible articles. Title and abstract reviews were conducted to identify relevant studies. Potential articles were then abstracted using a structured instrument and a serial review process by 2 investigators.RESULTS.Eighteen studies were eligible for review: 13 targeted healthcare providers, 3 targeted patients/participants, and 2 targeted both providers and patients. The study designs included randomized controlled trial, concurrent controlled trial, case‐control, descriptive, and qualitative. A lack of available protocols and/or a lack of provider awareness about clinical trials prevented providers from discussing the opportunity of clinical trials in 2 studies. In 14 studies, patient accrual was affected by provider attitudinal barriers relating to patient adherence to the study protocol, patient mistrust of research, patient costs, data collection costs, and/or patient eligibility. Providers' communication methods were barriers in 5 studies and promoters in 1 study.CONCLUSIONS.A heterogeneous body of evidence suggests that several provider‐related factors influence recruitment of underrepresented groups to clinical trials. Future recruitment efforts should address these factors. Cancer 2007;109:465–476. © 2007 American Cancer Society.