We describe the largest outbreak of measles in Central and Eastern Cheshire (North West England) since the MMR vaccine was introduced in 1988, the majority of cases were not vaccinated and more than 20% of the cases belonged to the travelling community. Over 4 months, 147 clinical cases of measles were notified locally to the Cheshire & Merseyside Health Protection Unit (CMHPU). Of these, 67 (45·6%) were laboratory confirmed, 42 (28·6%) were negative, and one was equivocal, leaving 23 probable and 14 possible cases. The primary case was probably an 8-year-old unvaccinated travelling child, symptomatic on 1 October 2008. Measles spread locally and within school-aged children until early February 2009. Most of Central and Eastern Cheshire, including 23 educational institutions (playgroups, nurseries, primary schools, secondary schools, colleges), were affected, showing that there were enough susceptible/unvaccinated children to sustain an outbreak. Nearly a quarter of the confirmed cases (15/67, 22·4%) were aged <13 months and too young to be vaccinated under the UK immunization schedule. This outbreak is a reminder of the importance of achieving herd immunity to prevent spread and protect those at risk of severe illness or complications. There were no fatalities in this outbreak and no significant complications were reported.