Background: Hashimoto's thyroiditis (HT) is the most common cause of hypothyroidism and is characterized by gradual autoimmune mediated thyroid failure with occasional goiter development. HT is seven times more likely to occur in women than in men. Papillary thyroid cancer (PTC), the most prevalent form of cancer in the thyroid, is 2.5 times more likely to develop in women than men. Given the relatively high prevalence of these diseases and the increased occurrence in women, we analyzed data from our institution to determine if there is a correlation between Hashimoto's thyroiditis and PTC in women. Methods: From May 1994 to January 2007, 1198 patients underwent thyroid surgery at our institution. Of these, 217 patients were diagnosed with HT (196 women, 21 men). The data from these patients were statistically analyzed using SPSS. Results: PTC occurred in 63 of 217 (29%) HT patients and 230 of 981 (23%) patients without HT (P = 0.051). Of these groups, 41 (65%) and 158 (69%) patients, respectively, had tumor sizes ≥1.0 cm; 56/196 women (29%) with HT had coexistent PTC compared with 160/730 women (22%) without HT (P = 0.03). Among women with any type of thyroid malignancy, 56/59 cases (95%) with HT had PTC compared with 159/196 cases (81%) in women without HT (P = 0.006). Additionally, female HT patients with goiters had a significantly lower rate of PTC (9% versus 36%, P < 0.001) compared with women without goiters. These differences were not observed in men with HT. Conclusions: These data demonstrate that HT is associated with an increased risk of developing PTC. Female patients with HT undergoing thyroidectomy are 30% more likely to have PTC. Thus, more aggressive surveillance for PTC may be indicated in patients with HT, especially in women. © 2008 Elsevier Inc. All rights reserved.