The Proteomics Shared Resource provides state-of the-art biological mass spectrometry analyses to cancer researchers at NYU to help them identify and characterize proteins of medical importance. In many cases, it is only by studying proteins directly that one can achieve a useful understanding of the processes that underly the functioning of cells and tissues in normal and diseased states such as cancer. The shared resource has the capability to identify single, hundreds or even thousands of proteins in a single analysis, often at subfemtomole levels, by state of the art liquid chromatography-tandem mass spectrometry followed by database searching or de novo sequence determination. In most cases the facility strives to obtain accurate information about the absolute and/or relative quantities of these proteins from cells under various conditions to obtain important information about the functioning of the proteins. The shared resource also has special expertise in characterizing posttranslational modifications of proteins such as phosphorylation, acylation, glycosylation and ubiquitination. In addition to its technical expertise, one of the strengths of the facility is its ability to advise clients in the design and interpretation of experiments so that useful data can be obtained and meaningful information can be had from these data. Reliance on cutting edge technology and its expert and dedicated staff allow these services to be performed in a cost effective manner. Indeed, many experiments by investigators at NYU and the NYU Cancer Institute (NYUCI) could not have been done without the assistance of the Shared Resource. The Resource also has established a Clinical Proteomics Core for the detection of protein and peptide biomarkers for the early detection of cancer.