This study assessed oral health status for preschool-aged children in the Navajo Nation to obtain data on baseline decayed, missing, and filled tooth surfaces (dmfs) and dental caries patterns, describe sociodemographic correlates of children's baseline dmfs measures, and compare the children's dmfs measures with previous dental survey data for the Navajo Nation from the Indian Health Service and the National Health and Nutrition Examination Survey (NHANES). Methods: The analyzed study sample included 981 child/caregiver dyads residing in the Navajo Nation who completed baseline dmfs assessments for an ongoing randomized clinical trial involving Navajo Nation Head Start Centers. Calibrated dental hygienists collected baseline dmfs data from child participants ages 3-5 years (488 males and 493 females), and caregivers completed a basic research factors questionnaire. Results: Mean dmfs for the study population was 21.33 (SD = 19.99) and not appreciably different from the 1999 Indian Health Service survey of Navajo Nation preschool-aged children (mean = 19.02, SD = 16.59, P = 0.08). However, only 69.5 percent of children in the current study had untreated decay compared with 82.9 percent in the 1999 Indian Health Service survey (P 0.0001). Study results were considerably higher than the 16.0 percent reported for 2-4-year-old children in the whites-only group from the 1999-2004 NHANES data. Age had the strongest association with dmfs, followed by child gender, then caregiver income and education. Conclusion: Dental caries in preschool-aged Navajo children is extremely high compared with other US population segments, and dmfs has not appreciably changed for more than a decade. (author abstract)