A UK-wide database of structured asthma review consultations was used to investigate the prevalence of 'off-label' anti-asthma prescriptions in relationship to clinical symptoms of asthma control. The 1050 children (6.1%) aged 16 years or under issued with an off-label prescription reported more nighttime, daytime and activity asthma symptoms, and used more short-acting beta(2)-agonist medication than their peers. Off-label prescribing for children with asthma in UK primary care is associated with worse levels of self-reported asthma control.