The effects of larval densities of one to four individuals in standard Drosophila-vials (diameter 25 by 95 mm) on the age at pupation, starved dry weight, and wing length of Culex pipiens quinquefasciatus Say were studied. This approach required relatively few larvae per replicate and included a control treatment, where individual larvae developed in the absence of competition. This design also tested for competitive interactions between male and female larvae. Mosquitoes pupated later, and emerged with lighter starved dry adult weight and shorter wings as larval density increased. The size of adult female mosquitoes, particularly their starved dry weight, was sensitive to larval density and also was influenced by the presence or absence of competition with another female larva. In contrast, the life history traits of males did not vary as a function of competition with female larva. Female larvae were also more likely to die in the highest density treatment. This design confirmed previous results and offered a potentially useful experimental approach to investigate the effects of density-dependent competition among mosquito larvae.