Cystic fibrosis (CF) is an autosomal-recessive disorder and affects about 60,000 people worldwide. The CF gene, the cystic fibrosis transmembrane conductance regulator (CFTR), was found in 1989 and over 800 mutations have been sequenced. Although our understanding of the pathophysiology of CF has increased, pulmonary infections remain the major cause of morbidity and mortality. During the first decade of life, Staphylococcus aureus and nontypable Haemophilus influenza are most common, but Pseudomonas aeruginosa may be the first pathogen isolated in infants. By 18 years of age, 80% of patients harbor P. aeruginosa and 3.5% harbor Burkholderia cepacia. Stenotrophomonas maltophilia, Achromobacter xylosoxidans, and nontuberculous mycobacteria may be newly emerging CF pathogens. The traditional approach to managing patients with CF is to treat acute pulmonary exacerbations with intravenous antimicrobial agents. However, prophylactic strategies to prevent initial infection or to delay chronic infection with P. aeruginosa or chronic maintenance therapy to slow deterioration of lung function may also improve clinical status. Recognition of the role of inflammation, even early in life, in the absence of clinical symptoms, has led to treatment with anti-inflammatory agents. Novel strategies to disrupt biofilm formation, stimulate chloride conductance, and replace abnormal CFTR are currently being studied.