The Australian Paediatric Surveillance Unit (APSU), through active surveillance, collects information on the epidemiology of rare or uncommon childhood conditions. This research resource allows paediatricians to collaborate at State, national and international levels. The APSU sends a monthly report card to all (currently 971) paediatricians in Australia, who in turn indicate whether or not they have seen a patient in the last month with any of the conditions listed (98% response rate in 1999). Study investigators, notified by the APSU of positive case reports, obtain demographic and clinical data on the patient from the reporting doctor by postal questionnaire (90% response rate in 1999). Since 1993, the APSU has monitored 27 conditions, including conditions that are vaccine-preventable, otherwise infectious, genetic, congenital and non-communicable. Information collected is disseminated to paediatricians and other health professionals via an annual report, newsletters and publications and is made available to the International Network of Paediatric Surveillance Units. Information provided by the APSU has raised awareness among paediatricians of rare and uncommon childhood conditions, and has been used by health authorities for planning of prevention and intervention strategies and allocation of health resources.