IMPORTANCE The incidence of thyroid cancer detection has increased by 4.5%per year over the last 10 years, faster than for any other cancer, but without a corresponding change in the mortality rate. In 2013, the incidence rate of thyroid cancer in the United States was 15.3 cases per 100 000 persons. Most cases of thyroid cancer have a good prognosis; the 5-year survival rate for thyroid cancer overall is 98.1%. OBJECTIVE To update the US Preventive Services Task Force (USPSTF) recommendation on screening for thyroid cancer. EVIDENCE REVIEW The USPSTF reviewed the evidence on the benefits and harms of screening for thyroid cancer in asymptomatic adults, the diagnostic accuracy of screening (including neck palpation and ultrasound), and the benefits and harms of treatment of screen-detected thyroid cancer. FINDINGS The USPSTF found inadequate direct evidence on the benefits of screening but determined that the magnitude of the overall benefits of screening and treatment can be bounded as no greater than small, given the relative rarity of thyroid cancer, the apparent lack of difference in outcomes between patients who are treated vs monitored (for the most common tumor types), and observational evidence showing no change in mortality over time after introduction of a mass screening program. The USPSTF found inadequate direct evidence on the harms of screening but determined that the overall magnitude of the harms of screening and treatment can be bounded as at least moderate, given adequate evidence of harms of treatment and indirect evidence that overdiagnosis and overtreatment are likely to be substantial with population-based screening. The USPSTF therefore determined that the net benefit of screening for thyroid cancer is negative. CONCLUSIONS AND RECOMMENDATION The USPSTF recommends against screening for thyroid cancer in asymptomatic adults. (D recommendation).