Context: Migrant and seasonal farmworkers are a population at risk for oral health problems. Data on the oral health conditions of migrant and seasonal farmworkers' permanent teeth are particularly lacking. Purpose: To document the relative rates of treated and untreated dental decay in a sample of southern Illinois migrant and seasonal farmworkers who had sought care at a farmworker health center dental clinic. Methods: Existing migrant health dental clinic records from 1995-2002 were reviewed. Final sample size was 650. Data for decayed, missing, and filled tooth surfaces were recorded using both anatomical recording and treatment notes. Findings: Sixty-nine percent of migrant farmworkers had at least 1 decayed (untreated) tooth surface, and more than half had 3 or more decayed surfaces. Conclusions: Results indicate that untreated dental decay is significant among migrant and seasonal farmworkers who seek care at this dental clinic. Recommendations include addressing barriers to care, improved monitoring of dental health conditions, and further research to better document the treatment needs of this population.