Adult mosquito size may be related to longevity, feeding frequency, and other factors that impact vectorial capacity. Various investigations have shown that characteristics of larval mosquito habitats influence adult size. We studied breeding container characteristics in relation to size and abundance of Aedes aegypti larvae and pupae in Iquitos, Peru, and compared these with the size of resulting adult females. During 22 May to 20 July 2000, immature mosquitoes were collected from 12,722 containers in 2,931 houses, of which 424 held ≥1 Ae. aegypti. A subsample of larvae and all 16,433 pupae detected was removed for study. Resting adult mosquitoes were also collected from the same houses as the immatures. Adult mosquito size was determined by measuring the wing lengths of 672 aspirated adults and 2,316 adult females that emerged from container-derived pupae. Immatures were most commonly found in rain-filled containers, located outside of houses, and without lids. The average wing length of females derived from pupae varied considerably (1.67–3.83 mm), with slightly less variation for females captured as adults (1.80–3.23 mm). Linear regression showed that average wing length of pupae-derived females was positively associated with presence of larvae, container-filling method, diameter of container, and density of females. Size of pupae-derived females was correlated with that of females captured in the same houses as adults. The geographic distribution of pupae and adults indicated that the spatial pattern for Ae. aegypti is heterogeneous, with areas of higher and lower abundance. These findings provide insight for more focused control efforts aimed at reducing Ae. aegypti-borne pathogens.