An outbreak of acute keratoconjunctivitis in an ophthalmology department affected 15 patients and seven members of staff and necessitated temporary closure of the unit. Adenovirus (Ad) was isolated from eye swabs taken during the outbreak, but typing of the isolates by virus neutralisation assay proved unsatisfactory, wrongly assigning the isolate to serotype 10. A robust and rapid method for preparing microgram amounts of Ad DNA from infected cells was devised and used as the basis of a non-radioactive method for routine genotyping of adenovirus clinical isolates. All isolates associated with the outbreak, and one from a patient presenting at a nearby hospital during the outbreak, were found to have restriction endonuclease digestion patterns characteristic of Ad 37.