Non-small cell lung cancers with neuroendocrine differentiation (NSCLC-NE) may demonstrate biologic behavior intermediate between non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) with impact on prognosis. We studied the expression of four well-defined neuroendocrine (NE) markers: neuron-specific enolase (NSE), chromogranin A, Leu-7, gastrin-releasing peptide, and a panel of three non-NE markers, including vimentin, and the epithelial markers carcino-embryonic antigen (CEA) by immunohistochemistry, and mucin by histochemistry in 237 resected NSCLCs from patients on six LCSG protocols. Twenty-nine (12%) tumors were positive for 2 or more NE markers. An NE differentiation score was calculated but failed to correlate with recurrence as did other combinations of markers. However, the presence of tissue staining for CEA was strongly associated with improved survival (p = 0.011), whereas the presence of mucin was associated with a worse outcome (p < 0.001). Individually, CEA and mucin remained prognostic even when corrected for stage, histologic features, and performance status. We conclude that NE differentiation is not predictive of recurrence in patients with resected NSCLC but data on patterns of CEA and mucin expression may improve prognostication and permit rational design of new therapeutic approaches.