Impact of Delta Opioid Receptor Gene (OPRD1) Variations on Treatment Outcome in African Americans

Background: \- Differences in peoples genes can make them respond to drugs in different ways. Methadone and buprenorphine are two drugs used to treat drug addiction. A study showed that African Americans with a certain genetic marker did better using one kind of drug treatment over the other. Researchers want to see if they can repeat these findings. They also want to study other things that affect how well people do in treatment. Objective: \- To see if certain genetic markers and other facts about a person s life can predict how well they do in treatment for addiction to opioids and cocaine. Eligibility: \- African American adults age 18 and over. They must be former or current participants in an Archway Treatment Clinic study. They must have been on a stable dose of either study drug for at least 12 weeks. They also must have given urine samples regularly for at least 10 weeks. Design: * Participants will come to the clinic for 1 visit lasting about 2 hours. * Participants will give 1 teaspoon of blood for genetic testing. They will be asked if their sample can be used in future studies. * If researchers cannot get enough blood, they will do a cheek swab. This will collect skin cells for genetic testing. * Participants will fill out 3 questionnaires. * Results of genetic testing and answers to questionnaires will be kept private.