Tissue microarray (TMA) is a recently implemented, high-throughput technology for the analysis of molecular markers in oncology. This research tool permits the rapid assessment of a biomarker in thousands of tumor samples, using commonly available laboratory assays such as immunohistochemistry and in situ hybridization. Although introduced less than a decade ago, TMA has proven to be invaluable in the study of tumor biology, the development of diagnostic tests, and the investigation of oncologic biomarkers. This review describes the impact of TMA-based research in clinical oncology and its potential future applications. Technical aspects of TMA construction and the advantages and disadvantages inherent to this technology are also discussed.