Tissue microarrays (TMAs) are used to simultaneously study the expression of proteins in hundreds of tissue samples, offering the important advantage to screen large tissue banks for biomarker expression and to simultaneously examine serial sections obtained from the same tumor specimen by a time- and cost-effective analytical approach. This review article presents an overview of the importance and the impact of this technique in cancer research with increasing number of investigations using TMAs in its eighth anniversary. Its application, limitations, and selected previous study results regarding urologic malignancies are presented and discussed.