Conceptually, the suggestion by Alifano et al1(August 2004) is especially compelling from both the scientific and clinical observational standpoints. However, one needs to carefully consider if low-molecular-weight heparins (LMWHs) are the best choice of drugs to conduct such an important study. First, not all LMWHs are the same, and hence should not be lumped together as one group.2Second, and more importantly, there is strong scientific evidence that the biological activities of heparins, beyond anticoagulation, including activities such as antineoplastic, antiangiogenetic, and antiinflamatory, are related to the molecular weight of heparin or more precisely to the high sulfate to carboxylate ratio of heparin (unfractionated heparin [UFH] is more heavily sulfated than LMWHs and has thus the highest ratio). This has been observed in relation to the cellular release of tissue factor pathway inhibitor, the down-regulation of vascular endothelial growth factor and endothelial growth factor, and the inhibition of the c-fos gene, reverse transcriptase, telomerase, and topoisomerase, as examples.6 The clear advantages of LMWHs relate to their predictable pharmacokinetics and the convenience of being able to administer the drug subcutaneously in an outpatient setting without the need for routine monitoring. In terms of efficacy and safety LMWHs and UFH are equivalent. While LMWH will provide for equivalent anticoagulation to UFH, we may lose an opportunity to grasp the real usefulness of the parent drug (UFH) from which the LMWHs have been sliced.