This special issue brings together articles that reflect 12 years of experience in the National Drug Abuse Treatment Clinical Trials Network (CTN), with methodological and statistical issues that arise in the design and conduct of controlled, multi-site, community-based effectiveness trials. To date, the CTN has randomized over 13,000 patients into 27 completed trials, with more trials currently ongoing, providing a wealth of experience in design, implementation, and analysis of effectiveness trials.

• The Design and Analysis of Multisite Effectiveness Trials: A Decade of Progress in the National Drug Abuse Clinical Trials Network [editorial] by Edward V. Nunes.
• Ten Take Home Lessons from the First 10 Years of the CTN and 10 Recommendations for the Future by Kathleen Carroll, Samuel Ball, Ron Jackson, et al.
• NIDA's Clinical Trials Network: An Opportunity for HIV Research in Community Substance Abuse Treatment Programs by Susan Tross, Aimee N. C. Campbell, Donald Calsyn, et al.
• Is Monogamy or Committed Relationship Status a Marker for Low Sexual Risk among Men in Substance Abuse Treatment? Clinical and Methodological Considerations by Donald Calsyn, Aimee N. C. Campbell, Susan Tross, and Mary Hatch-Maillette.
• Gender Research in the National Institute on Drug Abuse National Treatment Clinical Trials Network: A Summary of Findings by Shelly Greenfield, Carmen Rosa, Susan Putnins, et al.
• Comparative Profiles of Men and Women with Opioid Dependence: Results from a National Multisite Effectiveness Trial by Sudie Back, Rebecca Payne, Amy Herrin Wahlquist, et al.
• Conducting Research with Racial/Ethnic Minorities: Methodological Lessons from the NIDA Clinical Trials Network by A. Kathleen Burlew, Jerren C. Weekes, La'Trice Montgomery, et al.
• Research Partnerships between Academic Institutions and American Indian and Alaska Native Tribes and Organization: Effective Strategies and Lessons Learned in a Multisite CTN Study by Lisa Rey Thomas, Carmen Rosa, Alyssa Forcehimes, and Dennis Donovan.
• Determining the Primary Endpoint for a Stimulant Abuse Trial: Lessons Learned from STRIDE (CTN 0037) by Madhukar Trivedi, Tracy Greer, Jennifer Sharpe Potter, et al.
• Power of Automated Algorithms for Combining Time-Line Follow-Back and Urine Drug Screening Test Results in Stimulant-Abuse Clinical Trials by Neal Oden, Paul VanVeldhuisen, Paul Wakim, et al.
• Assessing Drug Use During Follow-Up: Direct Comparison of Candidate Outcome Definitions in Pooled Analyses of Addiction Treatment Studies by Jeffrey Korte, Kathryn Magruder, Codruta Chiuzan, et al.
• Zero-Inflated and Hurdle Models of Count Data with Extra Zeros: Examples from an HIV-Risk Reduction Intervention Trial by Mie-Chen Hu, Martina Pavlicova, and Edward Nunes.
• Some Considerations for Excess Zeroes in Substance Abuse Research by Dipankar Bandyopadhyay, Stacia DeSantis, Jeffrey Korte, and Kathleen Brady.
• Modeling Site Effects in the Design and Analysis of Multi-Site Trials by Daniel Feaster, Susan Mikulich-Gilbertson, and Ahnalee Brincks.
• An Exploration of Site Effects in a Multisite Trial of OROS-Methylphenidate for Smokers with Attention Deficit/Hyperactivity Disorder by Lirio S. Covey, Mei-Chen Hu, Carla Green, et al.
• Site Selection in Community-Based Clinical Trials for Substance Use Disorders: Strategies for Effective Site Selection by Jennifer Sharpe Potter, Dennis Donovan, Roger Weiss, et al.
• How Practice and Science are Balanced and Blended in the NIDA Clinical Trials Network: The Bidirectional Process in the Development of the STAGE-12 Protocol as an Example by Dennis Donovan, Dennis Daley, Gregory Brigham, et al.
• Design of NIDA CTN Protocol 0047: Motivational Assessment, Referral, and Treatment in Emergency Departments (SMART-ED) by Michael Bogenschutz, Dennis Donovan, Bryon Adinoff, et al.
• Relation of Study Design to Recruitment and Retention in CTN Trials by Paul Wakim, Carmen Rosa, Prasad Kothari, and Mary Ellen Michel.
• Standardized Patient Walkthroughs in the National Drug Abuse Treatment Clinical Trials Network: Common Challenges to Protocol Implementation by Holly Fussell, Lynn Kunkel, Dennis McCarty, and Colleen Lewy.
• Strategies for Safety Reporting in Substance Abuse Trials by Robert Lindblad, Maria Campanella, David Styers, et al.
• Baseline Matters: The Importance of Covariation for Baseline Severity in the Analysis of Clinical Trials by Edward Nunes, Martina Pavlicova, Mei-Chen Hu, et al.
• Participant Characteristics and Buprenorphine Dose by Maureen Hillhouse, Catherine Canamar, Geetha Doraimani, et al.
• Rates and Influences of Alcohol Use Disorder Comorbidity among Primary Stimulant Misuing Treatment-Seekers: Meta-Analytic Findings Across Eight NIDA CTN Trials by Bryan Hartzler, Dennis Donovan, and Zhen Huang.
• Smoking Cessation Treatment among Patients in Community-Based Substance Abuse Rehabilitation Programs: Exploring Predictors of Outcome as Clues Toward Treatment Improvement by Malcolm Reid, Huiping Jiang, Bryan Fallon, et al.