Our multicenter study is one of the largest involving a homogeneous group of Caucasian, non-squamous NSCLC patients treated with front-line chemotherapy based on pemetrexed and platinum and who had simultaneous analysis of up to five different polymorphisms in TS, MTHFR and ERCC1 genes. The gene discussed is MTHFR; the disease is non-small cell lung carcinoma.