The completion of the genomic sequence and the definition of the genes provide a wealth of data to interpret cellular protein expression patterns and relate them to protein function. Proteomics is the large-scale study of proteins in the post-genomic era, aimed at identifying and characterizing protein expression, function, posttranslational modification, regulation, trafficking, interaction and structure, and their perturbation by disease and drug action. The multigenetic background and essentially unknown etiology of hypertension, makes this main killer a prime candidate for proteomic analysis. The classical proteomic approaches are based on twodimensional gel electrophoretic protein separation and their subsequent identification and characterization by mass spectrometry analysis. However, expression level analysis may not reflect the functional state of proteins and is biased towards long-lived abundant proteins. This review describes a variety of techniques that can be used to identify low-abundance proteins that may be of more functional interest. The modification of classical two-dimensional electrophoresis in order to study post-translational modifications, e.g., phosphorylation, is also discussed.