Apatites originated from three Brazilian regions (craton of Sao Franci
sco, region situated between the craton of Sao Francisco and Parana ba
sin and oriental border of the Parana basin) were studied using the fi
ssion track method. Thermal histories were obtained applying to our ex
perimental data the theoretical model named ''Apatite Fission Track An
alysis'' and the ''Inverse Method'' with slight modifications.