Purpose: There are no nationally representative data on oncologists’ use of next generation sequencing (NGS) testing in practice. The purpose of this study was to investigate how oncologists in the U.S. use NGS tests to evaluate cancer patients and inform treatment recommendations. Methods: The study used data from the National Survey of Precision Medicine in Cancer Treatment, which was mailed to a nationally-representative sample of oncologists in 2017 (N=1,281; cooperation rate=38%). Weighted percentages were calculated to describe NGS test use. Multivariable modeling was conducted to assess the association of test use with oncologist practice characteristics. Results: Overall, 75.6% of oncologists reported using NGS tests to guide treatment decisions. Of these oncologists, 34.0% used them “often” to guide treatment decisions for patients with advanced refractory disease, 29.1% to determine eligibility for clinical trials, and 17.5% to decide on off-label use of FDA-approved drugs. NGS test results informed treatment recommendations “often” for 26.8%, “sometimes” for 52.4%, and “never” or “rarely” for 20.8% of oncologists. Oncologists <50 years of age, holding a faculty appointment, having genomics training, seeing more than 50 unique patients per month, and having access to a molecular tumor board were more likely to use NGS tests. Conclusion: In 2017, most U.S. oncologists were using NGS tests to guide treatment decisions for their patients. More research is needed to establish the clinical utility of these tests, develop evidence-based clinical guidelines for their use in practice, and ensure that patients who can benefit from these new technologies receive appropriate testing and treatment.