OBJECTIVES: To examine inpatient utilization among patients with cystic fibrosis (CF) and homozygous for the F508del CFTR gene mutation. METHODS: Medical chart data from patients with CF ≥12 years old were collected in France, Germany, Italy, Spain, Australia and Canada.  Demographics and clinical characteristics were obtained for a 12-month baseline period and a follow-up period ranging from 2-36 months.  Proportions of patients hospitalized, hospitalization rates, and length of stay were assessed overall and by age (12-17, ≥18 years), lung function (percent predicted forced expiratory volume in 1 second [ppFEV] ≥70%, 41-69%, ≤40%), and country. RESULTS: Data for 523 patients were included. Baseline mean ± SD age was 24.8 ± 9.5 years and mean ± SD ppFEVwas 67.1 ± 22.9%.  Over a mean of 27 months follow-up, 19% of patients had 1 hospitalization, 11% had 2, and 37% had ≥3. The mean ± SD rate of hospitalizations was 1.2 ± 1.5 per patient-year.  In the follow-up period, the proportion of patients with at least 1 hospitalization and the rate of hospitalization were highest for the severe ppFEVgroup relative to moderate and mild groups (86%, 73%, and 55% and 2.1 ± 2.0, 1.4 ± 1.6 and 0.7 ± 1.1 per patient-year respectively).  The overall mean length of stay was 10.7 ± 7.5 days; it was 9.2 ± 6.8 days for the mild lung function group vs 11.0 ± 6.7 days for the severe group.  The hospitalization rate ranged from 0.6 ± 1.1 per patient-year in Spain to 1.7 ± 1.9 in Australia; trends by lung function were consistent across countries. CONCLUSIONS: Patients with CF and homozygous for the F508del CFTR gene mutation have high rates of hospitalization. Hospitalization rate varies by country, but is consistently higher for patients with the lowest lung function, congruent with a progressive disease.