A 40-yr-old Hispanic man presented to NJCIRM with end-stage lung disease. Evaluation of this patient 10 yr earlier noted bronchiectasis, normal sweat electrolytes, pancreatic sufficiency, delayed progression of pulmonary disease, and a sperm biopsy consistent with fertility. At the time of admission bronchiectasis was extensive. DNA testing demonstrated homozygosity for the 3849+10kb C > T cystic fibrosis (CF) allele. This is the first description of homozygous expression of this allele in a male patient. Confirmation of fertility was established by demonstrating that his children were carriers of this allele. This patient emphasizes the importance of DNA testing for atypical CF alleles in patients with bronchiectasis of undetermined cause even in the presence of fertility, normal pancreatic function, and normal sweat electrolytes.