This research was carried with the objetive of evaluating the localization of Alternaria alternata, A. dauci and A. radicina spp. in the different parts of carrot seeds, as well as in the seed residues, the behavior of two carrot cultivars when inoculated with these fungi and the effect of different seed treatments on the disease control. Tegument, endosperm, embryo and seed debris were evaluated. The Alternaria spp., recovered from these seed parts, were grown in pure culture and inoculated on leaves of carrot plants, cultivars Brasília (resistent) and Nantes (susceptible). Carrot seeds collected from primary and from secondary umbels, were treated with iprodione, procymidone and hot water. The seeds were sown on sterilized soil and mainteined under greenhouse conditions. It was observed that Alternaria dauci is more commonly found associated with the embryo and endosperm. The species A. alternata and A. radicina were more prevalent on the pericarp. The three Alternaria species were also associated with the seed debris; therefore, such debris may serve as inoculum sources. Alternaria dauci and A. radicina caused severe symptons when inoculated on carrot plants of both cultivars tested. Alternaria alternata were pathogenic to carrot, but caused less severe symptons, as compared with other species. There was no damping-off on the plots sown with chemically-treated seeds. The higer rates of emergence as observed on these plots. The treatment with hot water was less efficient than those with fungicides, and it did not differ from the control, with the exeption of the plots with seeds from primary umbels.