['A total of 33 hospitals in 13 countries in North America, Europe, Africa, Asia and Latin America.', 'To investigate the relationship between the pneumonia severity index (PSI) and the time to clinical stability from intravenous to oral antibiotic therapy in hospitalized adult patients with community-acquired pneumonia (CAP).', 'An international, retrospective, observational study of random adult patients meeting the definition of CAP between June 2001 and May 2004.', 'The risk class (RC) according to the PSI was calculated for all patients. The criteria to define when a patient is clinically stable were evaluated daily during the first 7 days of hospitalization in all patients. The mean time to clinical stability for 254 patients in RC I was 4.2 days, for 233 patients in RC II it was 3.9 days, for 395 patients in RC III it was 4.6 days, for 644 patients in RC IV it was 5.0 days and for 296 patients in RC V it was 6.0 days. Significant positive correlations were observed between RC and time to clinical stability (P < 0.0001).'] Does the pneumonia severity index predict time to clinical stability in patients with community-acquired pneumonia?