Dengue fever (DF) and dengue haemorrhagic fever (DHF) pose a constant serious risk and continue to be a major public health threat in Thailand. A better understanding of the factors responsible for this affliction will enable a more precise prediction of the location and time of high-risk events. Mapping spatial distribution of disease occurrence and risk can serve as a useful tool for identifying exposures of public health concern. A Geographical Information System (GIS)-based methodology to investigate the relationship between the reported incidence of dengue fever and spatial patterns in nine districts of northern Thailand was analysed for the years 1999 to 2003. From the average prevalence of dengue cases in each district in different years, it is apparent that 2001 had the highest values, followed by 2002, 1999, 2000 and 2003 in that order. With Moran's I and Geary's Ratio, only the year 2001 showed spatial patterns with statistical significance.