This issue reviews the current status of scientific dream study and offers the most up-to-date reviews on topics such as dream recall (including variables affecting dream recall, and the psychopathology of altered dream recall), dream content (including the assessment of dream content and variables affecting dream content), dreaming and cognitive functions (dreaming and emotional processing, personality and psychopathology, and learning and memory), disordered dreaming (such as nightmares in patients with post-traumatic stress disorder, dreaming epiphenomena of narcolepsy, and parasomnias), medications altering dreaming, and the role of dreams in psychotherapy. Because sleep and dreams are inextricably linked, it is important for every sleep specialist to have an understanding of the current scientific understanding of normal and disordered dreaming.