We evaluated legislation introduced into Victoria in 1991 requiring that all children enrolling in primary school certify their immunisation status. Information was requested from all local councils. All primary schools in two local government areas were followed up, providing an indication of the validity of the analysis obtained from data collected during the mid-year census. From 166 of 210 local councils in Victoria, 48,422 documents relating to school entry immunisation certificates were issued for children entering their preparatory year. At least 522 children were enrolled in school on an undertaking to complete immunisation, and were likely to have had their immunisation completed as a result of the legislation. Only 170 statutory declarations of conscientious objection to immunisation were made, indicating that few parents are willing to express firm anti-vaccine sentiments. Compliance with the immunisation certificate legislation is overestimated by the mid-year census because many schools have accepted nonstatutory evidence of immunisation. Mobile and immigrant families find it particularly difficult to achieve certification. Local councils are inconsistent in the way in which they issue certificates. Further follow-up and feedback is essential to better inform schools and parents about the legislation. Such follow-up can improve the certification rates of children then and in subsequent years. The legislation has imposed a considerable workload on councils, but without efforts to improve compliance with the legislation and to develop practical guidelines for documentation of immunisation and appropriate guidelines regarding transfer, many inadequately immunised children may remain at risk from vaccine-preventable diseases.