Objective: To ascertain the distribution of alpha 1 antitrypsin genotypes and correlate it with the severity of pulmonary disease in patients with cystic fibrosis. Method: A clinical and laboratory cross sectional study of 70 patients at the Universidade Estadual de Campinas teaching hospital. Cystic fibrosis diagnoses was confirmed by both clinical and laboratory methods. The severity of cystic fibrosis was evaluated by Shwachman score. All the patients were tested for the presence of S and Z alleles for alpha 1 antitrypsin deficiency using polymerase chain reaction. Results: Nine (12.8%) patients were heterozygous for S or Z alleles or the heterozygote compound (SZ). No significant differences were found in clinical severity of Cystic fibrosis between genotypes of alpha 1 antitrypsin. No significant differences were found when the patients were divided according to the presence or absence of the DF508 mutation. Conclusion: In this study, the first undertaken in Brazil into the association of alpha 1 antitrypsin deficiency and cystic fibrosis, we did not find an association between the deficiency and cystic fibrosis severity. 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