Pemetrexed is an antimetabolite antineoplastic agent that exerts its action by inhibiting three enzymes-thymidylate synthetase (TS), glycinamide ribonucleotide formyltransferase (GARFT) and dihydrofolate reductase (DHFR), which are essential for the synthesis of purine and pyrimidine. It causes arrest of tumor cells in S phase of the cell cycle, thus inhibiting their growth.Pemetrexed has been approved as first-line treatment in malignant pleural mesothelioma and second-line treatment in non-small-cell lung cancer (NSCLC). This paper summarizes the current developments in the treatment of NSCLC.