Dihydrofolate reductase is an enzyme involved in the production of pyrimidinic base timidin, a structural component of DNA, therefore whatever substance that inhibit this enzyme inhibit the DNA synthesis as a consequence and it can be potentially useful as a treatment of several types of cancer like lymphoblastic leukemias. In this work we determinate the inhibition grade that the ethanol extracts from Colombian marine sponges: Svenzea zeai, Amphimedon compressa, Ircinia campana, Aplysina archeri, Xestospongia proxima y Xestospongia muta , over the human purified enzyme dihydrofolate reductase. The results shown that most of marine sponge extracts inhibite the enzyme. Results are compared with methotrexate® a medicament used against cancer which is used as a control for the bioassays. Results demonstrate that some of the analyzed extracts have more inhibition than the control metotrexate®.