The Measles Control Campaign (MCC) conducted in Australia from August to November 1998 resulted in a total of 1.7 million school children being vaccinated. This article reports on the Adverse Events Following Immunisation (AEFI) associated with measles-mumps-rubella vaccine (MMR) administered as part of the MCC. Reports of adverse events that occurred within 30 days of administration of the MMR vaccine were assessed by an expert panel that assigned a causality rating to each AEFI. Reports with missing onset dates or uncertain causality were excluded. Eighty-nine AEFI were classified as associated with MMR vaccine and the overall rate of adverse events was 5.24 per 100,000 doses of vaccine administered. Of these 46 were thought to be certainly caused by MMR vaccine, 23 were probably and 20 were possibly associated with the vaccine. Although 46 reactions were categorised to be certainly caused by the MMR vaccine, the majority of these were syncopal fits, syncope, local reactions, and allergic reactions that were short-lived, and all of these children recovered. The most commonly occurring adverse reaction was syncopal fit with a rate of 1.24 per 100,000. There was only one anaphylactic reaction, giving a rate of 0.06 per 100,000. The combined rate for anaphylaxis, anaphylactoid and allergic reactions was 1.06 per 100,000 administered doses. The rate of seizures (febrile and afebrile) was 0.30 and encephalopathy was 0.06 per 100,000 doses administered. Of the 89 children who had an AEFI, 43 did not require hospitalisation or medical attention while 13 were seen in an emergency room, 14 were hospitalised and 19 were seen by a doctor. There were no deaths reported resulting from the administration of the MMR vaccine during the period of the campaign. All children who had an AEFI have recovered although 9 children could not be followed up for reasons of confidentiality. The overall rate of adverse events was lower than that observed in the 1994 measles campaign conducted in the United Kingdom. On comparing the risks and benefits of MMR vaccine, the benefits of this MCC far outweigh the incidence of serious adverse events associated with immunisation.