Background: Substance use disorders (SUDs), which include substance dependence or abuse, have a tremendous impact on individuals, families, communities, and governments. This report highlights the number of American adults with SUDs in the past year and trends in SUDs between 2002 and 2014. Method: This report uses data from the 2002 to 2014 National Surveys on Drug Use and Health to examine trends in SUDs and receipt of treatment for substance use between 2002 and 2014. Results: Approximately 20.2 million adults aged 18 or older had a past year SUD. Of these adults, 16.3 million had an alcohol use disorder and 6.2 million had an illicit drug use disorder. An estimated 2.3 million adults had both an alcohol use disorder and an illicit drug use disorder in the past year. Of the adults with a past year SUD, 4 out of 5 had an alcohol use disorder, nearly 3 out of 10 had an illicit drug use disorder, and 1 out of 9 had both an alcohol use disorder and an illicit drug use disorder. The percentage of adults with a past year SUD in 2014 was similar to the percentages in 2010 to 2013 but was lower than the percentages in 2002 to 2009. Conclusion: Monitoring trends in SUDs gives public health providers opportunities to assess the scope of the issue in the United States and to plan substance abuse prevention and treatment programming. Most SUDs in the United States are related to alcohol use, and the long-term trends indicate that there has been a decrease in the prevalence of past year alcohol use disorders among adults. Although illicit drug use disorders are less prevalent than alcohol use disorders among adults, the long-term trends in this report indicate that there has not been a reduction in the percentage of adults who had an illicit drug use disorder in the past year.