Electronic laboratory reporting can improve surveillance for notifiable conditions. Building on standards for message structure and content, we have implemented an electronic laboratory reporting system by building on the infrastructure created for the Indiana Network for Patient Care (INPC). The system has proven reliable in delivering results and scalable to multiple laboratories over 36 months of use. In April 2000, the system identified over 1,000 cases of notifiable conditions from the laboratories at four different laboratories. Our experience in developing the system has highlighted the need for improved compliance with HL7 result message formats by the laboratory information systems and more structured reporting of results for tests such as microbiology including consistent use of the abnormal flag.