The pemetrexed disodium (Alimta), LY231514) is the first antifolate able to inhibit at the same time the synthesis of purins and pyrimidins. Many therapeutic tests were carried out in clinical situations where the methotrexate and the fluorouracil had been the proof of their effectiveness. It then showed an interesting activity in a great number of tumours but with very different profiles of tolerance according to the studies and pathologies. The explanation will come in 2001 by the description from the relation between the vitamin deficiencies among treated patients and occurred from toxicities. The two randomized studies carried out in the malignant pleural mesothelioma and the non small cell lung cancer made it possible to establish its utility and to record the pemetrexed in these clinical situations. Others axes of development remain possible, but the results are stanby or to confirm as in squamous-cell cancer in the head and neck and breast, digestive or urinary tracts cancer. In all the cases, the optimization of the pemetrexed in terms of amount/methods of administration and associations possible because of its profile of tolerance makes of it a molecule of chemotherapy with a future.