Background: The objective of this study was to define the epidemiology of thyroid cancer in our regional population and compare results with Surveillance, Epidemiology, and End Results (SEER) Program cancer registry trends.Methods: Thyroid cancer cases diagnosed between 1990 and 2000 were identified in the Florida Cancer Data System (FCDS). Overall, gender-specific, age-specific, and stage-specific incidence rates were calculated. All rates are per 100,000 and age-adjusted to the 2000 U.S. standard population. Estimated Annual Percent Change (EAPC) was calculated with a linear least-squares model.Results: Patients with thyroid cancer (n = 8603) were identified in the FCDS registry. Age-adjusted incidence rates increased from 4.2 per 100,000 to 7 per 100,000 in 2000. The EAPC for this period was 5.5% (P < .001). The SEER incidence rates increased from 7.9 to 10.2 per 100,000, and the EAPC was 3.7% (P < .05). Analysis of gender-specific incidence rates showed increases from 6 and 2.2 per 100,000 in 1990 to 10.1 and 3.8 per 100,000 in 2000 among females and males, respectively, with EAPCs of 5.9% (females) and 4.5% (males) (P < .001). With stratification by age group, the highest incidence rates were 9 per 100,000 in the group aged 65 to 84 years and 8.4 per 100,000 in the group aged 45 to 64 years.Conclusions: Thyroid cancer incidence rates in Florida almost doubled over the 1990–2000 period and are concordant with SEER trends. Etiologic studies addressing temporal changes in reproductive factors, more intensive diagnostic activities, and changes in histological criteria are warranted.