Cough is the fifth most common reason for physician visits, but data on acute cough have rarely been collected in a standardized manner and have not been analyzed in a multivariate fashion. We report data on 1819 patients presenting with cough, all of whom received a standardized history and physical, and a chest X-ray. Only 48 (2.6%) were found to have an acute radiographic infiltrate (pneumonia). The prevalence of common signs and symptoms is shown for the patients with and without pneumonia. Thirty-two of these findings were significant predictors of pneumonia (p less than 0.05, one-tailed). These 32 did not include some of the expected predictors of pneumonia and did include some predictors not previously described in the literature. A diagnostic rule is developed which identifies pneumonia patients with 91% sensitivity and 40% specificity, or 74% sensitivity and 70% specificity. The study results suggest that many pneumonias could be predicted based only on the patients histories. Physician visits to determine physical findings and chest X-rays might be avoided by telephone triage, with substantial cost savings.