Background A retrospective analysis of clinical data were conducted reviewing patients who were given erlotinib at Peking Union Medical College (PUMC) Hospital from May 2005 to December 2009. Relationships between clinical factors, epidermal growth factor receptor (EGFR) mRNA expression, EGFR gene mutations, KRAS gene mutations and clinical outcomes were investigated in Chinese patients with advanced non-small cell lung cancer (NSCLC). Methods Patients with stage ⅢB/Ⅳ NSCLC who had not previously participated in erlotinib related clinical trials were enrolled into this study. All patients were given oral erlotinib 150 mg per day. Tumor samples of some patients were accessed with mutant-enriched polymerase chain reaction assay (EGFR, KRAS gene mutations) and multiplex branched DNA assay (EGFR mRNA expression).Results Seventy-nine patients were enrolled in this study, 23 patients had a partial response (PR), 36 patients had a stable disease (SD), 20 patients had a PD, with an objective response rate of 29.1%, and a disease control rate of 74.7%.Females (P=0.023), non-smokers (P=0.013), patients with a skin rash (P=0.047), and with highly differentiated tumors (P=0.037) were significantly correlated with the objective response rate. Patients with a lower ECOG PS (P=0.002),highly differentiated tumors (P=0.014), non-smokers (P=0.002), and patients with a skin rash (P ＜0.001) were significantly correlated with the disease control rate. The median progression-free survival was 35 weeks (95% CI: 13-57 weeks) and 1-year survival was 72.3%. Highly-differentiated tumors (P=0.027) and patients with a skin rash (P ＜0.001)were significantly correlated with PFS. Seventeen patients were tested for EGFR/KRAS gene mutations and EGFR mRNA expression. Progression-free survival (PFS) of patients with EGFR exon 19/21 mutations was 66 weeks, longer than patients with wild type EGFR exon 19/21 (P=0.018). No significant relationships were found between EGFR mRNA expression, EGFR exon 19/21 mutations, and KRAS mutations and objective response rate or disease control rate. The most common adverse events were skin rash (60.9%) and diarrhea (26.6%).Conclusions Erlotinib was safe and effective in treating Chinese patients with advanced NSCLC. The PFS of patients who had a skin rash, highly differentiated tumors, or EGFR exon 19/21 mutations was significantly longer.