Stimulants are a key element in the treatment of ADHD. Carefully designed trials of stimulants have found substantial improvement in ADHD core behaviours in 65-75 % of subjects with ADHD. Most standard stimulants are rapidly absorbed, with their behavioural effects appearing within 30 minutes, reaching a peak within one to three hours and disappearing within five hours. Doses at school are often necessary, in spite of the risk of peer ridicule and added adult supervision requirements. The mechanism by which stimulants act to reduce hyperactivity is not completely understood, but they improve impulsivity and activity levels. Several controlled evaluations made over periods of time greater than a year show a clear persistence of medication effects over time. A carefully crafted programme of treatment with methylphenidate is more effective in the reduction of hyperactivity symptoms than an intensive programme of behavioural and cognitive intervention. The combination of stimulants with psychosocial interventions in ADHD offers few advantages over medication alone. Unchallengeable guides to practice that would be appropriate everywhere are difficult to propose. It is imperative that clinicians prescribing stimulants should monitor the use of the drug properly, making sure that it is not being abused by the child's family, peers or those dispensing medication at school. Polypharmacy should only be embarked on by a specialist service and the combination of methylphenidate and clonidine should be used cautiously. Apart from ADHD, stimulants are useful in narcolepsy, resistant depression and partial syndromes of attention and hyperactivity. Major gaps in knowledge remain; pharmacokinetics, pharmacodynamics and pharmacogenetics of stimulant effects need further study. Details of stimulant administration regimes seem to have a major effect on the response achieved. Further research is needed, preferably in realistic practice settings, comparing different forms of combination with psychological interventions, investigating the effects in groups of children outside the core of schoolaged children with typical ADHD: preschool children, adults, those with partial syndromes (such as inattentiveness) and those with co-morbid disorders.