The Australian Paediatric Surveillance Unit (APSU) conducts active national surveillance of conditions affecting children, including communicable diseases and their complications. By mailing over 900 clinicians each month the APSU gathers national information, not available from other sources, about the incidence, demographic and clinical features of these conditions. In some conditions APSU data supplements that available from existing schemes. The APSU has monitored 20 conditions to date. Eight of these are communicable diseases or their complications, two have a possible infectious aetiology and one frequently presents with infection. Since its inception in 1993 the return rate of monthly report cards by the mailing list has increased from 88 per cent to 94 per cent. Return rate of questionnaires for the communicable diseases studied ranged from 74 per cent to 100 per cent. Studies have enabled estimation of disease incidence, identification of risk factors and possible preventive strategies and provision of detailed clinical information. Although the APSU cannot serve a public health role by case identification and contact tracing it provides information that contributes to the communicable disease strategy for Australia.