There has recently been a resurgence of interest in Sluggish Cognitive Tempo (SCT) as an important construct in the field of abnormal child psychology. Characterized by drowsiness, daydreaming, lethargy, mental confusion, and slowed thinking/behavior, SCT has primarily been studied as a feature of Attention-Deficit/Hyperactivity Disorder (ADHD), and namely the predominately inattentive subtype/presentation. Although SCT is strongly associated with ADHD inattention, research increasingly supports the possibility that SCT is distinct from ADHD or perhaps a different mental health condition altogether, with unique relations to child and adolescent psychosocial adjustment. This introductory article to the Special Section on SCT provides an historical overview of the SCT construct and briefly describes the contributions of the eight empirical papers included in the Special Section. Given the emerging importance of SCT for abnormal psychology and clinical science, there is a clear need for additional studies that examine (1) the measurement, structure, and multidimensional nature of SCT, (2) SCT as statistically distinct from not only ADHD-inattention but also other psychopathologies (particularly depression and anxiety), (3) genetic and environmental contributions to the development of SCT symptoms, and (4) functional impairments associated with SCT. This Special Section brings together papers to advance the current knowledge related to these issues as well as to spur research in this exciting and expanding area of abnormal psychology.