Susceptibility tests were carried out in laboratory conditions to evaluate the efficacy of alpha-cypermethrin (a synthetic pyrethroid never used in Côte d'Ivoire) for malaria vector control. Five wild populations of Anopheles gambiae originating from M'bé, Yaokoffikro, Korhogo, Kafiné and Daola and two laboratory reared strains (Kisumu susceptible and Kou permethrin resistant selected strain) were tested. The diagnostic dosage of alpha-cypermethrin for the sensitive strain Kisumu was 2.5 x 10(-3)%. A comparative study of the susceptibility of samples of wild populations of An. gambiae was carried out according to the WHO standard susceptibility test. Impregnated papers with 4% DDT, 0.25% permethrin, 0.025% deltamethrin and 0.0025% alpha-cypermethrin were used. The results showed that except for mosquitoes from M'bé, all the other populations were resistant to these insecticides. Bioassays were carried out with alpha-cypermethrin at the operational dosage of 20 mg a.i./m2 on the same population and laboratory reared strains. The results showed the efficacy of this insecticide on both the Kisumu strain and the population from M'bé, a maintained efficacy for the Daloa, Kafiné and Korhogo mosquito populations, but the wild anopheline population from Yaokoffikro clearly appeared fully resistant.