Measles is uncommon in Australia due to effective national vaccination strategies. In mid-2003, a cluster of nine cases of measles occurred in western Sydney. The index case was a 29-year-old traveller recently returned from Nepal. The case presented to hospital and transmitted the disease to two others in the Emergency Department. Further cases resulted from both community and nosocomial transmission. The median age of cases was 24 years, with three cases in children aged under four years. Only one person had a documented history of measles vaccination, a child who had received one dose of vaccine overseas. One case was a 2-month-old infant whose mother was immune and two cases were hospital staff members. Molecular analysis of measles virus isolates from four cases revealed the same D8 genotype, a strain previously identifi ed in Nepal. Staff vaccination strategies implemented as a result of the outbreak were poorly patronised despite nosocomial transmission. As diseases such as measles become rare it is important to thoroughly investigate any outbreaks, and to maintain a high index of suspicion of measles, particularly in travellers presenting with a rash having returned from measles-endemic areas. Genetic analysis is important in tracing the origins of an outbreak, and to confi rm relatedness between cases. The highly infectious nature of measles virus also underscores the need for appropriate infection control in minimising risk of nosocomial transmission. Such policies are of increasing importance with the emergence of novel viruses or the threat of pandemic infl uenza.