BACKGROUND: Recruitment and retention in clinical trials of minorities is low, particularly in rural underserved populations. This has slowed progress in addressing racial/ethnic disparities in oral health. PURPOSE: To describe factors associated with successful recruitment, and identify predictors of continued retention of pregnant women attending a community health center into a randomized controlled clinical trial to prevent early childhood caries. METHODS: The Mothers and Youth Access (MAYA) Trial recruited women in the second trimester of pregnancy. At baseline, consenting women completed an oral health questionnaire and received a dental exam and oral health counseling. Four months postpartum, women returned with their babies for randomization with follow up at 9-, 12-, 18-, 24-, 30-, and 36-month postpartum visits. To assess predictors of retention, data about respondents' demographics, and oral health-related knowledge, attitudes, and behaviors were obtained by questionnaire and analyzed by logistic and discrete time-to-event regression analyses. RESULTS: Of 556 predominantly Mexican-American women recruited at baseline, 195 (35%) were excluded after baseline for not meeting inclusion criteria; 361 (65%) continued to randomization. Factors such as race/ethnicity, annual household income, household composition, oral health-related knowledge and behaviors significantly related to retention until randomization. In multivariable models, women reporting a higher annual household income were less likely to be lost to attrition before randomization (odds ratio = 0.73, 95% confidence interval (CI) 0.60-0.89); while Mexican/Mexican-American women were less likely to be lost beyond randomization (hazard ratio = 0.53, 95% CI 0.26-1.08). LIMITATIONS: Factors not measured at baseline may have been important in predicting attrition. The MAYA Trial is expected to finish by November 2008; therefore, complete results for total retention may differ from those reported here. CONCLUSIONS: Recruitment and retention efforts for pregnant Hispanic women should place heavy emphasis on culture as ethnicity remained the only borderline significant predictor in postrandomization retention.