This publication is based on the discussions and recommendations arising from an expert consultation, jointly organised by the FAO, the World Organisation for Animal Health (OIE), and the Canadian Federal Department of Fisheries and Oceans, held in Rome in October 2002. It contains technical information on the design of scientifically valid zonation frameworks for disease control and surveillance, aimed at providing advice to countries building national or regional aquatic animal health management infrastructures. It includes a case study of the Atlantic Canadian oyster disease surveillance programme, which was implemented to deal with a disease outbreak which occurred at the same time as the expert meeting was being held.