The mossaico-das-nervuras forma "Ribeirão Bonito", also called "cotton blue disease", is a highly important virus disease for the cotton crop, because of its field severity which provoques direct production losses and the excessive insecticide control costs of the aphid vector, Aphis gossypii. In order to reduce production costs, environment impacts and to increase economic gain for the cottongrowers, Coodetec and Cirad, since the beginning of the breeding program in 1990, have developed blue disease resistant or tolerant varieties. Aiming the study of the CD 401 variety resistance inheritance to the blue disease, F1, F2:3 e RC1Fi populations, derived from CD 401 X FM 966 crosses, were evaluated. Using a greenhouse test, artificially virus-inoculated plants - by cotton aphids bred in infected plants- were identified as resistant or susceptible. A segregation analyze was carried out by a qui-square test The obtained results indicate that the cotton blue disease resistance, in the case of CD 401 variety, is express for two dominant and independent genes, with duplicated effect.