The objective of this study was to evaluate the effect of vector control and elimination of infected dogs on the incidence of infection with Leishmania chagasi. A randomized community intervention trial was carried out in Teresina between 1995 and 1996. The area was divided in 34 blocks randomically allocated to 4 types of intervention: 1) spraying houses and animal pens with insecticide; 2) spraying houses and eliminating infected dogs; 3) combination of spraying houses and animal pens, and eliminating infected dogs, and 4) only spraying houses. In comparison to blocks receiving only household spraying, culling dogs decreased in 80% the incidence of infection. Spraying animal pens, associated or not with culling dogs, showed no significant effect. The protection offered by culling dogs suggests that this strategy might reduce the source of infection for the vector.