The improved knowledge of the key molecular mechanisms involved in cell transformation and tumor progression allows to the identification of new therapeutic targets for anticancer therapy. Several molecular-targeting compounds have been developed, capable to selectively interfire with tumorangiogenesis, receptors with tyrosin-chinase activity, specific tumor growth factors. A rationale selection of the patients as well as an appropriate monitoring of pharmacodynamics effects of molecular-targeting compounds need of the availability of surrogate markers, assessable in tumor tissue of circulating blood.