Attention-deficit hyperactivity disorder (ADHD) is probably the most common chronic undiagnosed psychiatric disorder in adults. It is characterized by inattention and distractibility, restlessness, labile mood, quick temper, overactivity, disorganization, and impulsivity. It is always preceded by the childhood diagnosis, a disorder that is rarely inquired about, and usually overlooked. Treatment can be dramatically effective. Approximately two thirds of adult ADHD patients experience moderate-to-marked improvement with psychoeducational management and stimulant drug therapy.