Predicting who will develop cancer and how the cancer will behave and respond to therapy after diagnosis are some of the potential benefits of the ongoing genetic revolution that can be envisioned within the next decade. Translational applications of genomic-based research efforts may actually precede the development of effective therapeutic agents that can exploit the vast amounts of data derived from these efforts. In the future, understanding the wealth of information generated by high-throughput molecular efforts and how it can be applied to clinical problems will likely be critical to the surgeon who guides the multidisciplinary care of the cancer patient. This review will discuss the advances in our understanding of the human genome (DNA), its derived transcriptome (RNA), and its translated proteome (proteins) and will focus on the translation of this information into routine clinical practice. In particular, we will focus on the potential for clinical application of microarray-based gene-expression profiling to the diagnosis, prognosis, and therapy of malignancies.