A temporal and spatial study of malaria transmission in a suburban area of Maputo, Mozambique with a mean population density of 2,737/km2 was made from December 1992 to June 1995. A steep but continuous gradient was observed in the Plasmodium falciparum prevalence from 59.0% adjacent to the breeding sites to 5.4% only a few hundred meters distant. The entomologic inoculation rate ranged from a number too low to be determined in some districts to 20 infectious bites per person per year in the others. The risk of malaria was 6.2 times higher for individuals living less than 200 meters from the breeding sites than for individuals living 500 meters or more away from the breeding sites. In areas of high human density, mosquito and parasite dispersion is very limited, and therefore malaria control strategies could be more specifically targeted.