Substance use treatment; Outpatient; Outpatient methadone/buprenorphine or naltrexone treatment; Regular outpatient treatment; Methadone used in Treatment; Does not treat alcohol use disorder; Federally-certified Opioid Treatment Program; Methadone maintenance; Methadone; Brief intervention; Cognitive behavioral therapy; Motivational interviewing; Relapse prevention; Substance use disorder counseling; State government; State Substance use treatment agency; State mental health department; State department of health; Commission on Accreditation of Rehabilitation Facilities (CARF); SAMHSA certification for opioid treatment program (OTP); Drug Enforcement Agency (DEA); Federal, or any government funding for substance use treatment programs; No payment accepted; Payment assistance (check with facility for details); Young adults; Adult women; Adult men; Seniors or older adults; Clients with co-occurring mental and substance use disorders; Clients with HIV or AIDS; Comprehensive substance use assessment; Outreach to persons in the community; Screening for substance use; Professional interventionist/educational consultant; Drug and alcohol oral fluid testing; HIV testing; STD testing; TB screening; Discharge Planning; Outcome follow-up after discharge; Housing services; Assistance with obtaining social services; Employment counseling or training; HIV or AIDS education, counseling, or support; Hepatitis education, counseling, or support; Health education services other than HIV/AIDS or hepatitis; Substance use disorder education; Individual counseling; Group counseling; Family counseling; Smoking not permitted; Adults; Seniors; Young adults; Female; Male; Opioid use disorder clients only; Spanish; Vaping not permitted; Case management service; Domestic violence services, including family or partner; Early intervention for HIV; Social skills development