Over the past 30 years, there has been much research into the health benefits of humour and laughter. Although often viewed very positively, rigorous evaluation of the therapeutic effect of clowning is complex. Clowning is a multi-modal intervention, which may have an impact on medical conditions, procedures, family functioning and health care teams. Clowns help children to adapt to their hospital surroundings and can distract from, and demystify, painful or frightening procedures through 'doses of fun' to complement traditional clinical interventions. This paper provides a review of the paediatric literature and reveals studies looking at the effect of clown interventions on various practical procedures and individual medical conditions, and the effects of clowning within clinical teams.