Introduction: Regardless of epidermal growth factor receptor (EGFR) mutation status, erlotinib improves survival for patients with advanced non-small cell lung cancer (NSCLC) after one or more chemotherapy regimens. Enzastaurin is an oral serine/threonine kinase inhibitor. This phase II study was designed to evaluate the efficacy and safety of erlotinib and enzastaurin in NSCLC, a combination with promise to overcome EGFR resistance based on preclinical models. Methods: Eligible patients with advanced NSCLC (IIIB or IV) who had failed one or two prior systemic treatment regimen(s) were enrolled and received erlotinib 150. mg/day and enzastaurin 500. mg/day (after a 1125-mg loading dose on day 1, cycle 1), both orally in 28-day cycles. The primary endpoint was progression-free survival (PFS). Results: From January 2008 to July 2009, 49 patients were enrolled: 29 (59%) men and 20 (41%) women; 8 (16%) were non-smokers. The median PFS was 1.7. months (one-sided 90% CI: 1.5-NA) and median overall survival (OS) was 8.3. months (95% CI: 5.3-14.3). Five patients had partial response, for an overall response rate of 10.2%; the disease control rate was 30.6% (responders. +. 10 patients with stable disease). Grade 3-4 drug-related adverse events in ≥5% of patients were diarrhea, acne, and nausea. One possibly drug-related death due to interstitial lung disease occurred during the study. Conclusions: In previously treated, unselected, advanced NSCLC patients, the addition of enzastaurin to erlotinib did not improve PFS, response, or OS compared with historical data of single-agent erlotinib, but was well tolerated.