 Newer cross-sectional imaging methods allow improved visualization of anatomic detailfor example, high-resolution CT has a spatial resolution of less than 1 mm in all 3 dimensions. These imaging methods also provide a limited amount of physiologic informationfor example, tumor perfusion as demonstrated by enhancement with intravenous contrast agents. Radiologic-pathologic correlation in the current era gives us the opportunity to work on a finer spatial scale and to take advantage of the additional physiologic information. Pathologic assessment of tissue has evolved at the same time. Tissue can be stained in the traditional way for microscopic evaluation but newer tools such as immunohistochemistry and, most recently, methods of molecular biology can be applied as well. 