This chapter reviews the methods that have been used for the collection of animal health data then specifically examines three methods of data collection being used in the animal health information system by the Queensland Department of Primary Industries (QDPI). One method of passive data collection, namely laboratory submissions, and two active methods are considered. The laboratory database examined is maintained as part of the QDPI laboratory services. The active data have been collected as part of the system of Structured Animal Health Surveillance (SAHS) that is being set up in Queensland (Baldock, 1995) and the two methods considered are the collection of serum specimens from animals on-farm and the collection of serum specimens at an abattoir. The strengths and weaknesses of each method of data collection are examined in this chapter. In the case of laboratory data their use in estimating disease occurrence is examined. In the case of serological testing the usefulness in determining age specific seroprevalence of the two methods for the collection of specimens is compared.