This special issue represents an effort by the journal Experimental and Clinical Psychopharmacology to emphasize its interdisciplinary mission by encouraging the writing of articles on clinical research and the interchange between basic and clinical research on mental illness and the addictions. This special issue opens with a commentary from A. I. Leshner (2002), retired director of the National Institute on Drug Abuse, which emphasizes the importance of translating research findings into clinical practice. Four review articles and 12 original research reports provide a broad sampling of contemporary clinical research, including behavioral therapy, pharmacotherapy, psychiatric comorbidity, and special populations, and also illustrate linkages between clinical research and basic fields of inquiry, including behavioral theory, neuropsychology, neuropharmacology, and statistics.