OBJECTIVES: To identify local ecological factors that might have had an impact on the higher infestation rates by the vector mosquito Aedes aegypti seen in four urban health districts of Ciudad de La Habana, Cuba, and to determine the type of containers with the highest number of larvae. METHODS: This is a descriptive study that was carried out in four health areas (Docente, 28 de Enero, 26 de Julio, and 1. degrees de Enero) within Playa, a municipality belonging to Ciudad de La Habana, Cuba. These areas were chosen because of the persistent presence of the dengue vector throughout 2003. All buildings on the selected blocks were inspected between April 2004 and March 2005, and note was taken of existing water deposits (type, number, and location) and of surrounding ecological factors (existence of a patio and shade, the way tanks were covered, the presence of organic matter inside them, and the overall cleanliness of the dwelling). Using filtration, the mosquito larvae and pupae in each deposit were counted. Pupae were typified as to their taxonomic species under a stereoscopic microscope. RESULTS: The types of deposits where larvae and pupae of A. aegypti were most often found in all areas were low tanks and small artificial containers. In three of the study areas the greatest numbers of pupae were found in low tanks (88.6%, 100%, and 56.6%), 90.9% of which were uncovered or only partially covered. On the other hand, in the fourth study area small artificial deposits were the most commonly infested (85.7%). A correlation was noted between the number of deposits in infested houses and the presence of a patio (chi(2) = 29.59; P = 0.0001), partial shade (chi(2) = 4.108; P = 0.0001), shrubbery (chi(2) = 43.59; P = 0.0001) and trees (chi(2) = 101.459; P = 0.0001), as well as poor hygiene (chi(2) = 53.76; P = 0.0001). CONCLUSIONS: Artificial deposits, especially low tanks and small containers, are the most frequent breeding sites for A. aegypti and are therefore risk factors for infestation with this vector species. Uncovered tanks containing organic matter and located in the shade on the outside of homes were found to present the highest risk in this respect.