A study on dengue control was undertaken in a poor urban area in Cúcuta, Colombia. The first objective was to describe people's knowledge, attitudes and practices regarding dengue fever, the transmission of the disease and possible preventive measures. The second objective was to analyse the infestation of the community with Aedes aegypti larvae, and the third objective to test the efficacy of Bti (Bacillus thuringiensis israelensis) with respect to the level and duration of reduction of Ae. aegypti larvae in water tanks. It was found that people had a very fragmentary knowledge about dengue and about the necessary protective measures which did not lead them to any action. The infestation of water containers, particularly the larger tanks, was very high (house index = 61; Breteau index = 96). The application of Bti in water tanks led to satisfactory results: For one month and longer, the water tanks treated with Bti were free of mosquito larvae. The effect was reduced by a lower dose, washing the tanks and a less potent formulation. People's acceptance of Bti was higher than that of temephos. Further studies are necessary to confirm the utility of Bti in dengue control.