Proteomics is becoming an important research area for studying protein expression patterns induced by different external stimuli. An important aspect of proteomics is to identify and quantify proteins. Many new technologies and techniques have been developed in this field and have been applied to various aspects of drug discovery. Keywords: Proteomics, 2-D electrophoresis, high performance liquid chromatography (HPLC), isotope-coded affinity tag (ICAT), stable isotope labeling by amino acid in cell culture (SILAC), mass spectrometry (MS), drug discovery