Objective: To determine the complication and hospitalization rates in children with cystic fibrosis (CF) by mode of diagnosis. Study design: Newly diagnosed cases of CF were identified from the Cystic Fibrosis Foundation National Patient Registry for 2000 through 2002. Cases were categorized as symptomatic diagnosis (SYMP; n = 1760), prenatal diagnosis (PRE; n = 66), diagnosis by means of newborn screening (NBS; n = 256), or presentation with meconium ileus (MI; n = 484). Complications were defined for the calendar year of diagnosis as stunting (length < 3rd percentile), wasting (weight < 3rd percentile), positive Pseudomonas aeruginosa culture results, and hypoelectrolytemia or edema and hypoproteinemia. Results: For infants (age < 12 months), 70% of patients with SYMP had at least 1 complication or hospitalization, compared with 29% for patients with NBS diagnosis (P < .0001). Crosssectional data for 2002 showed that patients with SYMP had significantly more complications compared with patients with NBS diagnosis as old as 20 years. When compared with patients with NBS diagnosis, patients with SYMP had increased mucoid P aeruginosa (P < .05) and decreased pulmonary function as assessed by means of forced expiratory volume in 1 second (P < .01). Conclusions: SYMP of CF is associated with increased complication rates throughout infancy, childhood, and adolescence when compared with NBS diagnosis. Objective: To determine the complication and hospitalization rates in children with cystic fibrosis (CF) by mode of diagnosis. Study design: Newly diagnosed cases of CF were identified from the Cystic Fibrosis Foundation National Patient Registry for 2000 through 2002. Cases were categorized as symptomatic diagnosis of preborn diagnosis (SYMP; n = 1760), prenatal diagnosis (PRE; n = 66), diagnosis by means of newborn screening (NBS; n = 256), or presentation with meconium ileus the calendar year of diagnosis as stunting (length <3rd percentile), wasting (weight <3rd percentile), positive Pseudomonas aeruginosa culture results, and hypoelectrolyte or edema and hypoproteinemia. with SYMP had at least 1 complication or hospitalization, compared with 29% for patients with NBS diagnosis (P <.0001). Crosssectional data for 2002 showed that patients with SYMP had significantly more complications compared wi When compared with patients with NBS diagnosis, patients with SYMP had increased mucoid P aeruginosa (P <.05) and decreased pulmonary function as assessed by means of forced expiratory volume in 1 second (P <.01). Conclusions: SYMP of CF is associated with increased complication rates throughout infancy, childhood, and adolescence when compared with NBS diagnosis.