The American Cancer Society (ACS) initiated the Breast Cancer Dietary Intervention Project (BCDIP) to involve community volunteers in cancer-related intervention research activities focused on dietary fat reduction in women with breast cancer. This article presents data on the volunteer aspects of the project, with two aims: (a) to describe the volunteer recruitment and intervention designed for the BCDIP, conducted jointly by the American Cancer Society and the Fred Hutchinson Cancer Research Center, and (b) to present baseline characteristics and predictors of retention of the BCDIP volunteers. There were five types of volunteers, called volunteer adjunct researchers or VARs, in the BCDIP. VARs were recruited using a variety of approaches, including electronic media alerts, flyers in oncology clinics, and notices in the newsletters of state nursing and nutritional professional organizations. Over half of all VARs came from two main sources: the media (television, radio, newspapers) and from work-related sources. Over half (58%) of the VARs had professional licenses in nursing or dietetics, and 46% were employed full-time. Several types of motivations for participating in the BCDIP, including altruistic reasons (want to help others, help people with cancer), health concerns (family/friend with breast cancer, have had cancer), and work-related reasons (gain professional skills) were important. Sixty-eight percent of VARs remained with the project for its entirety. Predictors of retention in the VAR program included previous ACS volunteer experience with initial motivations to volunteer and the interaction of employment status and professional nursing training. In future research and community-based projects, better recruitment and volunteer coordination procedures should be used to reduce dropout rates and maintain volunteer commitment and participation.