The effects of temperature and larval density on survival of larvae, growth rate, age at pupation, and adult size (measured as wing length and dry weight) of laboratory-reared Anopheles gambiae (Diptera: Culicidae) were studied. Larvae were reared at three temperatures (24, 27 and 30 °C) and three densities (0.5, 1 and 2 larvae/cm2). The effects of density and temperature strongly interacted to determine the mosquitoes' life-history parameters. Survival was highest at the intermediate temperature of 27 °C. The differences between the temperatures increased with increasing density. At 30 °C survival decreased as density increased, but at 27 °C increasing density led to higher survival. Age at pupation increased as temperature decreased from 30 °C to 24 °C and as density decreased from 2 to 0.5 larvae/cm2. Adult size also increased as temperature decreased, but showed a negative correlation with density only at 27 °C. In contrast, at 24 °C and 30 °C a decrease in density led to a decrease in adult size. Growth rate showed a similar pattern. At 27 °C growth rate decreased as density increased, but at other temperatures the opposite trend was observed.