Purpose: This study aims to investigate the association between cell phone use and thyroid cancer. Methods: A population-based case control study was conducted in Connecticut between 2010 and 2011 including 462 histologically confirmed thyroid cancer cases and 498 population-based controls. Multivariate unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs) for associations between cell phone use and thyroid cancer. Results: Cell phone use was not associated with thyroid cancer (OR: 1.05, 95% CI: 0.74-1.48). A suggestive increase in risk of thyroid microcarcinoma (tumor size <= 10 mm) was observed for long-term and more frequent users. Compared with cell phone nonusers, several groups had nonstatistically significantly increased risk of thyroid microcarcinoma: individuals who had used a cell phone >15 years (OR: 1.29, 95% CI: 0.83-2.00), who had used a cell phone >2 hours per day (OR: 1.40, 95% CI: 0.83-2.35), who had the most cumulative use hours (OR: 1.58, 95% CI: 0.98-2.54), and who had the most cumulative calls (OR: 1.20, 95% CI: 0.78-1.84). Conclusions: This study found no significant association between cell phone use and thyroid cancer. A suggestive elevated risk of thyroid microcarcinoma associated with long-term and more frequent uses warrants further investigation. (C) 2018 Elsevier Inc. All rights reserved.