Techniques to describe and investigate clustering of disease in space Ð the nearest-neighbour test, autocorrelation, Cuzick-and-Edwards' test and the spatial scan statistic Ð and in time Ð the Ederer±Myers±Mantel test and the temporal scan statistic Ð are reviewed. The application of these techniques in veterinary epidemiology is demonstrated by the analysis of a data set describing the occurrence of blowfly strike Ð both body strike and breech strike Ð between August 1998 and May 1999 in 33 commercial sheep flocks located within two local government areas of southeastern Queensland, Australia. By applying a combination of these methods, the occurrence of blowfly strike in the study area is well-characterised in both space and time. Guidelines for investigating disease clusters in veterinary epidemiology are discussed. # 2000 Elsevier Science B.V. All rights reserved.