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Sequencing of all 27 CFTR exons, including flanking intronic regions, and a search for large rearrangements were undertaken in the remaining 18 DNA samples. Calling all the patients back for further familial genetic studies could not be considered and we assumed that two identified mutations are located in trans. ORs were calculated and proportions were compared with prior probability using the likelihood ratio test and assuming an expected carrier rate of 1/25 (4%) in the Belgian general population. Mean age (6SD) at the time of DNA sampling was 58.9 (614.2) years. Bronchiectasis were present in 14/18 patients. Sweat chloride values between 40e59 mmol/l and 30e39 mmol/l were observed in 1 (5.5%) and 6 patients (33%), respectively. A total of 18 putative mutations were identified in 17/36 alleles (table 1), most of which were mild/ uncommon. CFTR mutation carrier frequency was much higher in patients with ABPA (12/18, 67%) than expected in the general population (p < 0.0001; OR 48.0, 95% CI 5.2 to 445.3). The probability of bearing two CFTR mutations was even more strikingly different (p<0.0001; OR 714, 95% CI 75 to 6797). This study considerably extends previous findings by demonstrating a strong link between ABPA in adults and CFTR mutations. Although not altering the message, limitations of this work include the small population sizewhich is inherent to the rarity of ABPA, the absence of DNA testing in parents and the dilemma of the clinical relevance of putative CFTR mutations. The hitherto best studied CFTR-related disorders are congenital bilateral absence of the vas deferens (CBAVD) and idiopathic chronic pancreatitis (ICP). It has been estimated that 85% of patients with CBAVD and 30% of those with ICP carry at least one CFTR mutation while w50% and 10e15%, respectively, are compound heterozygous, with the F508del mutation and IVS8-T5 variant being most frequently detected. The present study supports the concept thatABPA inpancreaticsufficient adults is a CFTR-related disorder, with rare class IVeVmutations being mostly found and IVS8-T5 not seeming to play a significant role.Moreover, asABPA is usually associated with bronchiectasis, a major phenotypic feature of CF, appropriate investigations to exclude milder forms of CF are warranted in these patients.