A limited number of studies suggest an increased incidience of celiac disease (CD) in individuals with autoimmune thyroid disease. We sought to determine the prevalence of tTG-IgA antibodies associated with CD and the prevalence of CD in patients with autoimmune thyroid disease in the United States. Our results will also be compared with the results obtained in Europe. Methods: 50 pediatric patients with autoimmune thyroid disease participated in this study. After written informed consent was obtained, blood was drawn to determine their tissue transglutaminase IgA (tTG-IgA) levels and total IgA levels. If the tTG-IgA levels were positive, an endoscopy and biopsy were performed to confirm the diagnosis of CD. Results: Four of our patients (8%) had positive tTG-IgA. Of those, 3 underwent endoscopy. One (2%) of our patients was diagnosed with CD based on the histopathology using the Marsh Criteria. Two patients' biopsies were negative, and one patient refused endoscopy. Our results showed a lower correlation between autoimmune thyroid disease and CD than do the results from the European literature which showed a range from 14-40%. However, we did find a higher correlation (2%) of positive tTG-IgA in those patients with autoimmune thyroid disease than in the normal population in the US which is 0.4-0.9%. Discussion: European literature suggests that approximately 14-40% of their patients with autoimmune thyroid disease have CD. Eight percent of our patients had positive tTG-IgA which was significantly higher compared to normal populations. However, only 2% of our autoimmune thyroid patients also have CD. tTG-IgA positivity by itself should not be interpreted as diagnostic of CD. However, because there is a higher chance of having CD with autoimmune thyroid disease than those who do not, we also recommend measuring tTG-IgA levels in patients with autoimmune thyroid disease. This must be followed by histopathological examination for CD when tTG-IgA is positive.