Colonies of three strains of Aëdes aegypti resistant to DDT were obtained from Trinidad, Haiti and Malaya and reared beside a normal colony. From their relative resistance to a series of compounds analogous to DDT, characteristic resistance "spectra" were obtained. The two colonies from the West Indies showed a similar type of resistance, rather different from the (smaller) resistance of the Malay strain. No resistance to methoxychlor or dieldrin was found.