This Healthcare Cost and Utilization Project (HCUP) Statistical Brief presents statistics on inpatient stays involving dependence on, abuse of, and poisoning and adverse effects from opioids (e.g., prescription opioids, heroin) and stimulants (e.g., cocaine, psychostimulants, amphetamines). Data are from adults aged 18 years and older in the 2012–2014 and 2016–2018 National Inpatient Sample (NIS) and State Inpatient Databases (SID). National trends in opioid- and stimulant-related stays are shown from 2012 to 2014 and 2016 to 2018, overall and by primary expected payer. Additionally, characteristics of stays involving opioids and stimulants and State-specific rates of opioid- and stimulant-related stays are examined in 2012 and 2018. Because of the large sample size of the NIS and SID data, small differences can be statistically significant but not clinically important. Thus, only differences greater than or equal to 10 percent are discussed in the text.