The frequency of 62 different CFTR mutations in 225 chromosomes from a CF birth cohort, which includes all the affected subjects born in northeast Italy during a 10-year period of time, was investigated. New mutations were also searched by the analysis of 15 different exons. The total proportion of CF chromosomes with detectable mutations is 73.78%. Therefore although a considerable improvement in CF mutation detection in our population has been achieved, the search for other common and uncommon mutations should be continued. Moreover a carrier screening program should be postponed until reaching a cumulative proportion of known CF alleles of at least 90%. The correlations between the genotypes which have been identified and the main clinical features added some new information to the classification of CF mutations as pancreatically severe or mild ones.