Consensus does not exist regarding what should constitute a "dream disorder." Conditions with disordered dreaming may be thought of as primary (ie, arising from changes in dreaming per se) or secondary to extrinsic disorders that impinge on structures involved in dreaming. The major primary disorder of dreaming, nightmare disorder, is covered in depth in this article. Definition of nightmare, diagnostic criteria for nightmare disorder, and differential diagnosis are discussed. The value of a sleep-disorders perspective on nightmares, and the possible exacerbating effects of sleep disorders that cause arousals, are indicated. The importance of a perspective that appreciates nightmares as richly and personally meaningful, with links to complex psychological factors present and past, is emphasized. Two types of treatment approaches are discussed: approaches that target the symptom of nightmares in relative isolation, and approaches that aim at working out psychological issues viewed as causing nightmares and a variety of other interconnected symptoms and problems. The former type of treatment includes the cognitive-behavioral approach "imagery rehearsal therapy," and the medication prazosin. The latter approach entails exploratory or psychodynamic psychotherapies. The approaches are seen as so different in scope, aim, and conceptual framework as to defy ready comparison. I think that a thorough psychological/psychiatric evaluation is essential for informed consideration in conjunction with the patient's choice of treatment approach. Sleep terrors are discussed as a non-rapid eye movement sleep arousal disorder that at times may be linked to broader psychological issues warranting consideration of psychotherapy. Brief summaries are provided of dream disorders secondary to other sleep disorders, drug and alcohol effects, medical disorders, and organic brain damage.