This study examined the use of lay advocates (i.e., women enrolled in a study who advocate to others) to improve recruitment among Hispanic women in the Arizona recruitment sites for a large-scale, national prevention study, the Women's Health Initiative (WHI). We examined whether trained, Hispanic lay advocates (called Embajadoras) brought more women into the study than a matched group of Hispanic and Anglo enrollees in the WHI who were supplied with brochures. Fifty-six Hispanic participants in the WHI were randomized to receive training or no training on advocacy, and continued to meet quarterly for 18 months. Also, 42 Anglo women were assigned to control. All groups received brochures to use for advocating the WHI. The number of women referred and enrolled was tracked as well as other factors expected to influence outcomes. Embajadoras were more successful at referral and enrollment than untrained Hispanic women and more successful at enrollment than untrained Anglo controls. Embajadoras were also found to distribute significantly more brochures than control groups. Therefore, a culturally aligned training program to encourage current Hispanic participants in a clinical trial to advocate the study to others may be an effective way to boost referrals and enrollments. Other potential influences on enrollment or referral success could not be determined due to the small sample size. Further study is needed to examine the best methods to encourage enrollment for women referred to the study.