['Individuals with cystic fibrosis (CF) are subject to recurrent respiratory infections (exacerbations) that often require intravenous antibiotic treatment and may result in permanent loss of lung function. The optimal means of delivering therapy remains unclear.', 'To determine whether duration or venue of intravenous antibiotic administration affect lung function.', 'Data were retrospectively collected on 1,535 subjects recruited by the US CF Twin and Sibling Study from US CF care centers between 2000 and 2007.', 'Long-term decline in FEV₁ after exacerbation was observed regardless of whether antibiotics were administered in the hospital (mean, -3.3 percentage points [95% confidence interval, -3.9 to -2.6]; n = 602 courses of therapy) or at home (mean, -3.5 percentage points [95% confidence interval, -4.5 to -2.5]; n = 232 courses of therapy); this decline was not different by venue using t tests (P = 0.69) or regression (P = 0.91). No difference in intervals between courses of antibiotics was observed between hospital (median, 119 d [interquartile range, 166]; n = 602) and home (median, 98 d [interquartile range, 155]; n = 232) (P = 0.29). Patients with greater drops in FEV₁ with exacerbations had worse long-term decline even if lung function initially recovered with treatment (P < 0.001). Examination of FEV₁ measures obtained during treatment for exacerbations indicated that improvement in FEV₁ plateaus after 7-10 days of therapy.'] Do location and duration of treatment of cystic fibrosis respiratory exacerbations affect outcomes?