Optical spectroscopy has been extensively studied as a potential in vivo diagnostic tool that can provide information about both the chemical and morphologic structure of tissue in near real time. Most in vivo studies have concentrated on elastic scattering and fluorescence spectroscopies since these signals can be obtained with a good signal-to-noise ratio quickly. However, Raman spectroscopy, an inelastic scattering process, provides a wealth of spectrally narrow features that can be related to the specific molecular structure of the sample. Because of these advantages, Raman spectroscopy has been used to study static and dynamic properties of biologically important molecules in solution, in single living cells, in cell cultures, and more recently, in tissues. This article reviews recent developments in the attempt to develop diagnostic techniques for precancers and cancers, based on Raman spectroscopy. The article surveys important transformations that
occur as tissues progress from normal to precancer and cancerous stages. We briefly review the extensive
literature that summarizes the features and interpretation of Raman spectra of these molecules in solution, and in progressively more complex biological systems. Finally, spectra obtained from intact tissues are comprehensively reviewed and discussed in terms of the molecular and microscopic literature to develop a framework for analyzing Raman signals to yield information about the molecular changes that occur with neoplasia. The article concludes with our perspective on the potential role of Raman spectroscopy in diagnosing precancer and cancerous tissues.