Drug dependence is a condition in which drug seeking holds a higher priority than behaviors controlled by other reinforcers. Learning to understand, predict, and control this maladaptive choice behavior may lead to improved prevention and treatment strategies. HYD is a drug currently used as a cough suppressant and to relieve pain. The purpose of this study is to determine the extent to which opioid drug seeking behavior in heroin dependent individuals can be reduced by environmental factors, including supplemental opioid drug availability, drug price, and non-drug alternative reinforcers. Specifically, this study will determine whether pre-session opportunity to take "free" supplemental HYD influences HYD seeking by using a choice progressive ratio schedule as well as by varying the dose of HYD.