PREVIEW
Pneumonia that is slow to resolve after appropriate antibiotic therapy can be problematic. The sheer number of possible underlying conditions and diseases with similar respiratory signs and symptoms often seems overwhelming. These factors, along with a failure to appreciate how long it can take for pneumonia to resolve radiographically, sometimes lead to unnecessary invasive diagnostic procedures. In this article, the authors review the infectious and noninfectious causes of nonresolving pneumonia, immune defense factors, and approaches to judicious evaluation.