Background and objective Pemetrexed have been approved for the treatment of patients affected by advanced non-small cell lung cancner (NSCLC) in progression after first-line chemotherapy. We evaluated the activity and feasibility of pemetrexed in previously treated NSCLC.Methods Patients with histologically or cytologically confirmed NSCLC were evaluated from April 2007 to March 2009. The patients had relapsed or progressed after prior chemotherapy treatment. Pemetrexed (500 mg/m2) was administered intravenously once every 3 weeks after progression to prior chemotherapy. The tumor response was evaluated according to RECIST criteria by chest CT at every 2 cycles of chemotherapy.Results A total 61 patients were eligible for analysis. Performance status of them (100%) was over 2. The response rate and disease control rate were 14.7% and 37.7% respectively. Non-squamous cell carcinoma histology was significantly associated with a superior response rate (P=0.045) and disease control rate (P=0.008). The median survival time and the median progression free survival (PFS) time were 6.11 months and 2.17 months, respectively. Comparing the efficacy of pemetrexed in these two settings [second-line versus (12/61) more than third (49/61)], there was no significant difference in regard to median survival (11.18 months vs 11.46 months, P=0.922,S), but PFS was more longer in third- or further-line groups than second-line group (1.39 months vs 2.25 months, P=0.015,3).Conclusion Pemetrexed is a feasible regimen in previously treated NSCLC with poor performance status.