In the last few years there has been an increased effort into the separation, quantification and identification of all proteins in a cell or tissue. This is a review of the role gel electrophoresis, high performance liquid chromatography (HPLC), and capillary electrophoresis (CE) play in proteomics research. The capabilities and limitations of each separation technique have been pointed out. Instrumental strategies for the resolution of cell proteins which are based on efficient separation employing either a single high-resolution procedure or a multidimensional approach on-line or off-line, and a mass spectrometer for protein identification have been reviewed. A comparison of the advantages of multi-dimensional separations such as two-dimensional polyacrylamide gel electrophoresis, HPLC-HPLC, and HPLC-CE to the separation of cell and tissue proteins are discussed. Also, a discussion of novel approaches to protein concentration, separation, detection, and quantification is given.