Cystic Fibrosis (CF) is a potentially lethal recessive disease , and it is the most frequent genetic disease in Caucasian populations. Its incidence is variable and related to ethnic and geographical differences of the populations. At the moment 1338 mutations are known ,which, when in homozigosis, cause Cystic Fibrosis. The gene is located in the long arm of the chromosome 7, in the q31 locus coding a mRNA of 6,5 Kb, that transcribes a regulator protein transmembrane protein of the ionic transport, composed by 1480 amino acids, known as CFTR (Cystic Fibrosis Transmembrane Conductance Regulator).In this study, 275 individuals were analyzed. From among them, 260 were healthy individuals for the cystic fibrosis and 15 were part of two proband families. The DNA of leucocytes extracted was amplified using specific primers for the identification of the mutation with posterior digestion with restriction enzyme Dde I. It was visualized in poliacrylamide gel at 12%, with intronic primers that flank the area of the exon 19 of the gene CFTR. The mutation R1162X was not detected in none of the analyzed individuals, showing, consequently, a null frequency. The absence of the mutation R1162X in our data, can be basically explained by the ethnic composition of our population. The European Amerindian miscegenation with Italian origin should be not frequent as expected or may be the mutation was absent of the European immigrants that originated the migrants population, although the proband family of Triunfo had Amerindian and Italian origin.