In 1998, Trinidad experienced its first major outbreak of dengue haemorrhagic fever. Data from the Trinidad Public Health Laboratory, the National Surveillance Unit and Insect Vector Control Division, Ministry of Health, Trinidad and Tobago were analysed to determine the impact of vector control measures on the dengue outbreak. Geographical Information Systems (GIS)/Global Positioning Systems (GPS) were used to map cases and to distinguish epidemiological clusters. The Aedes aegypti population densities were higher than the 5% transmission threshold in all counties. The spatial distribution of dengue fever cases was significantly correlated with the heavily populated east-west corridor in the north and several distinctly separate clusters in the western part of the island. The temporal distribution patterns showed significantly more dengue fever cases occurring during the rainy season than during the dry season. This study documents the importance of vector control in the prevention of dengue transmission since no vaccine is currently available, and emphasizes the urgent need to understand better the environmental factors which contribute to the proliferation of this disease vector Ae. aegypti.