More patients with cystic fibrosis are surviving into adulthood. Primary care physicians need a basic understanding of adult cystic fibrosis and the evaluation of patients with acute decompensation. Respiratory decompensation is usually the result of infective agents, including Pseudomonas aeruginosa, Stentrophomonas maltophilia and Burkholderia cepacia, and requires treatment with intravenous antibiotics. If symptoms worsen, the possibility of another complication, such as pneumothorax, hemoptysis, mycobacterial infection and allergic bronchopulmonary aspergillosis, must be considered. Family physicians can play an important role in the birth to adult care of patients with cystic fibrosis.