Practitioners are increasingly called upon to diagnose and treat attention deficit hyperactivity disorder (ADHD) in adults. Although the use of pharmacotherapy in children with ADHD is well studied, the use of drugs for the treatment of adults with ADHD remains less well established.A systematic review of the literature identified 15 studies (n = 482 patients) of stimulants, and 27 studies of nonstimulant medications (n = 1179 subjects) including antidepressants, norepinephrine reuptake inhibitors, antihypertensive agents, amino acids and wake-promoting agents for the treatment of ADHD in adults. Controlled clinical trials in adults showed that stimulants, antidepressants and norepinephrine reuptake inhibitors demonstrated significant short-term improvements in ADHD symptoms compared with placebo. The two longer term trials with methylphenidate in adults confirmed the ongoing effectiveness and tolerability of stimulants. The response to amphetamine and methylphenidate appears to be dose-dependent. Methylphenidate and amphetamine had an immediate onset of action, whereas responses to pemoline, antidepressants and norepinephrine reuptake inhibitors appeared delayed. Controlled data on nicotinic/cholinergic compounds appear promising. Considerable variability was found in the diagnostic criteria for ADHD in adults, drug dosages and response rates between the various studies. Under controlled conditions, the aggregate literature comprised mainly of short-term studies, shows that stimulants, norepinephrine reuptake inhibitors and specific antidepressants had clinically and statistically significant beneficial effects in the treatment of ADHD in adults. Cholinergic agents appear promising. Further studies are necessary to evaluate the long-term effectiveness and tolerability of various agents, functional and neuropsychological outcomes, and the use of various agents in specific subgroups of adults with ADHD.