We use a case-based format to review 4 relatively common, diagnostic challenges in surgical pathology of nonneoplastic lung diseases. All cases are linked to virtual slides so that the reader can participate in a manner that simulates the breakout session held at the 2008 New Frontiers in Pathology course at the University of Michigan, from which, this material was excerpted. Brief clinical histories and a summary of radiologic findings are followed by a description of the pertinent histologic findings and a concise topic review, intended to focus on practical diagnostic considerations. Our goal is that readers gain a greater understanding of those features most helpful in recognizing usual interstitial pneumonia, Langerhans cell histiocytosis, aspiration pneumonia, and Wegener granulomatosis.