This study aimed to evaluate the effects of existing practices of residents in reducing pre-adult Aedes aegypti (L.) infestation and to assess the effect of dengue-related knowledge on the practices. A house-to-house survey was conducted in two areas with different socioeconomic status in Ho Chi Minh City between October and November 2007. Some residents in both the areas used covers on the productive containers such as the jars and plastic buckets (i.e., 58% and 81% in the two study areas), and it was effective in reducing Ae. aegypti infestation: odds ratio (OR) of 4.0 and 4.9 (95% confidence interval [CI]: 1.49-10.76 and 1.2-19.57, respectively) for the containers with inappropriate covers compared with those with appropriate covers in the two areas, respectively. Appropriate cover use was an effective practice; however, no beneficial role of the knowledge related to dengue in promoting the practice was identified.