The commonest adverse effects of methylphenidate and dexamfetamine are appetite suppression, weight loss and sleep disturbance, although sometimes sleep is improved. There can be a modest effect of stimulant medication on decreasing growth velocity, but even this can be avoided by regular monitoring and adjustment of dosage or preparation when needed. Tics are not a contraindication to stimulant medication but exacerbation of tics may warrant dose reduction or change of medication. Both stimulant medication and atomoxetine can increase blood pressure, but any increases are usually small. The risk of sudden death does not appear to be increased by stimulant medication. Routine ECGs are not recommended. Specialist opinion should, however, be sought before medication is commenced for patients with a relevant personal or family cardiac history. Baseline measurement and regular follow-up monitoring of blood pressure, pulse, height (in children) and weight are recommended for patients taking stimulant medication or atomoxetine. The potential for substance misuse is probably not increased by prescribing medication for ADHD. Psychotic symptoms are only rarely associated with ADHD treatment. Most of the adverse effects of licensed medication for ADHD are mild and/or easily reversible.