Metabolomics is the newest "omics" science. It is a dynamic portrait of the metabolic status of living systems. Metabolomics has brought new insights on metabolic fluxes and a more comprehensive and holistic understanding of a cell's environment. This burgeoning field promises to be a potential tool to fill the gap between genotype and phenotype. As its preceding "omics" sciences (ie, genomics and proteomics), metabolomics' aim is to dredge information hidden in a sea of data. This technology permits simultaneous monitoring of many hundreds, or thousands, of macro- and small molecules, as well as functional monitoring of multiple pivotal cellular pathways. In addition, elucidation of cellular responses to molecular damage, including evolutionarily conserved inducible molecular defense systems, could be achieved with metabolomics and could lead to the discovery of new biomarkers of molecular responses to functional perturbations. If metabolomic information could be translated into diagnostic tests, it might have the potential to impact on clinical practice, and it might lead to the supplementation of traditional biomarkers of cellular integrity, cell and tissue homeostasis, and morphological alterations that result from cell damage or death. In this review the concept and characteristics of metabolomics are introduced. Main current applications of metabolomics in cancer research are reviewed, including its potential in the drug discovery field, and, last but not least, its potential impact in the field of monitoring response and toxicity to anticancer agents. In the last section, research projects ongoing at our institution and future challenges for metabolomics will be presented and briefly discussed.