During the past several years, there has been an increase in the cases of urban malaria in Buenaventura, Colombia, from 576 in 1987 to 3296 in 1991 and 2017 in 1992; therefore, an epidemiological study to identify transmission patterns was carried out in this municipality on Colombia's Pacific coast. This paper describes the entomological findings regarding vectors, potential breeding sites and behavior of Anopheles species during the period from June 1993 to May 1994. Of the 469 potential breeding sites identified in the urban area, 28 were positive for anophelines, while in the neighboring rural zone, 20 out of 80 potential breeding sites were positive for the immature forms of Anopheles. Mining excavations, lakes and breeding ponds for fish or shrimp were the places where A. albimanus was more frequently found. For A. nuñeztovari, the breeding sites were rain puddles and ponds for breeding fish or shrimp. A. neivai was also identified in the urban area and larvae were collected from bromeliaceous plants. Both inside and outside the households mosquito collections were carried out, and 90% of the collected mosquitoes were identified as A. albimanus. Of the female A. albimanus 54.8% were parous. This species was found to have peak peridomiciliary activity between 6 p.m. and 10 p.m. The highest biting rate in the peridomiciliary area was 7.1 and was observed during March. It is expected that this entomological information will permit the launching of a strong community participation process and the implementation of control measures in accordance with the entomological findings related to malaria in the urban area of Buenaventura.