In this study, the activity of cyromazine was evaluated following WHO standard procedures against susceptible and resistant mosquito strains of Anopheles gambiae, Culex quinquefasciatus, and Aedes aegypti. The dose for 50% and 90% inhibition of adult emergence (IE₅₀ and IE₉₀) ranged from 0.028 mg/liter to 0.17 mg/liter and from 0.075 mg/liter to 0.42 mg/liter, respectively. The effects of cyromazine were closer to that of chitin synthesis inhibitors rather than that of juvenile hormone analogues, with only 10–20% pupal mortality. The toxicity of cyromazine was not strongly affected by the presence of common resistance mechanism, i.e., Kdr mutation and Ace.1^R (resistance ratio from 0.5 to 2.3). The absence of cross resistance with common insecticides (pyrethroids, carbamates, organophosphates) makes cyromazine a potential candidate for disease vector control, especially for the management of insecticide resistance.