For study purposes, OP swabs or expectorated sputum for bacterial culture will be obtained annually beginning in the calendar year of first isolation of Pa from a respiratory culture at the local site laboratory. A serum sample for serology assessment and banking will be obtained annually in conjunction with a scheduled clinical blood draw whenever possible. Under a separate consent, additional blood (6 ml) will be collected for DNA use and banking for studies of genetic factors that may be associated with CF pathogenesis, disease progression, and clinical outcomes. These studies will test for association between gene variants and various CF-related phenotypes using either a targeted (i.e., candidate gene) approach or by performing a whole-genome scan.