Chronic persistent cough (CPC) is a common symptom generally caused by postnasal drip syndrome (PND), bronchial asthma (A), chronic bronchitis (CB), and gastro-oesophageal reflux (GOR). The purpose of this study was to confirm the value of a testing protocol for determining the causes of CPC in adult patients and for evaluating the outcome of its specific therapy. Ninety-two patients with unexplained CPC were sent to our Department between January 1994 and June 1996. The mean (+/- SE) duration of cough was 32.7 (+/- 4.5) months. We studied these patients (number) by applying an anatomical protocol, according to which clinical evaluation they underwent: chest (92) and sinus (90) radiography, spirometry (92), methacholine inhalation challenge (88), skin prick tests (67), oesophagoscopy (28), prolonged oesophageal pH monitoring (14), and bronchoscopy (49), as needed. The results of the standardized specific therapy refer to 87 patients because 5 patients were lost to follow-up. Thus, CPC was due to: sinusitis or chronic rhinitis plus PND in 56% of patients, CB in 18%, A in 14%, GOR in 5%, PND and GOR in 6%, A and GOR in 1%. The cough went away in 79/87 patients after specific treatment, based on the diagnostic findings, giving a success rate of 91%. The results of the present study confirm previous findings indicating that one or more causes of chronic persistent cough can be found, and that an elevated success rate of therapy was reached when an anatomic diagnostic protocol was used.