Proteomics, as the study of the proteomes of tissues and body fluids, has recently been introduced as a tool for revealing urologic diseases. Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and surface-enhanced laser desorption/ionzation (SELDI) are two techniques used in proteomic studies. Among the many urologic diseases, the malignancies including prostate cancer, bladder cancer, and renal cancer are the subjects most often selected for proteomic analysis. Poor reproducibility is one of the difficulties that must be overcome in order for proteomic technology to be a robust tool.