Psychostimulants constitute the most efficacious drugs in the treatment of attention-deficit hyperactivity/impulsivity disorder (ADHD). This chapter explores the variety of alternative nonstimulant drugs in the treatment of adult ADHD. Despite the generally robust behavioral effects of tricyclic antidepressants (TCAs), they have weaker cognitive effects in ADHD than the psychostimulants and often leave significant residual attentional effects. The anti-ADHD effects of TCAs seem to be independent of their antidepressant effects. Atomoxetine is a specific norepinephrine transporter reuptake blocker that has minimal affinity for other receptors. Adults experienced significant improvements in ADHD symptoms and demonstrated improvements in executive functioning. Clonidine, which at low dosages stimulates the presynaptic alpha-2 adrenergic autoreceptors, has been largely abandoned in the treatment of core symptoms of ADHD. One small preliminary study using a randomized, double-blind, crossover design examined the efficacy of methylphenidate (MPH) and lithium in treating ADHD in adults.