Larvae of Chironomus crassicaudatus Malloch were reared individually at nine constant temperatures from 12.5 to 32.5°C (2.5°C increments) for 120 d. Duration of immature stages (egg, four instars, and pupa), head capsule width of fourth instars, and wing length were recorded. Some adults emerged at all temperatures, except at 12.5°C where individuals developed to fourth instars during the experiment. Sharpe and DeMichele’s four-parameter model with high-temperature inhibition described the temperature-dependent developmental rates. The slowest development was observed at 15°C, with developmental rate peaking between 25 and 27.5°C. Developmental rate increased rapidly with increasing temperature up to 20°C, slowed between 20 and 27.5°C, and decreased at temperatures >27.5°C. No developmental inhibition at high temperatures was observed in eggs. The most apparent high-temperature inhibition of development was recorded in fourth instars, which comprised the largest proportion of developmental time. Males developed faster than females, but females had wider larval head capsules and longer wings than males. Adult size was negatively related with temperature in both sexes, but this relationship was steeper in males than in females. Larval size peaked at 20°C, whereas the head capsule width was reduced at temperatures higher and lower than 20°C.