Using a diagnostic protocol based on the anatomy and distribution of cough receptors and afferent nerves, we sought to determine the causes and outcome of specific therapy of chronic persistent cough in 49 consecutive and unselected patients. A specific diagnosis was made in all. Cough was due to chronic postnasal dip from a variety of conditions in 29%, asthma in 25%, postnasal drip plus asthma in 18%, chronic bronchitis in 12%, gastroesophageal reflux in 10%, and miscellaneous disorders in 6%. History, physical examination, and methacholine inhalational challenge diagnosed disease in 86% of all patients. Adjusted success rates for specific therapy, and average of 4.4 and 18.9 months after therapy had been prescribed, were 98% and 97%, respectively. We concluded the following about chronic persistent cough; using an anatomic, diagnostic protocol, the cause can be consistently determined; postnasal drip and/or bronchial asthma are very common causes of cough; the outcome of specific therapy, almost without exception, is successful and sustained.