Four dimensional visualization (FDV) project for clinical angiography has started at National Cancer-Center since 1995 in cooperation with medical virtual reality projects in our center. All stereo pair of x-ray angiographic images, both digital images and film based conventional x-ray images, are available in this system. FDV system software was developed on a Silicon Graphics platform. Every stereo pair angiographic images can be viewed stereoscopically using a stereoscopic visualization interface. Series of image data sets provide three dimensional blood flow dynamics that is very useful to diagnose vascular encasement by the tumor and to determine vessel of purpose which locates in front or in back from superimposed angiographic images. FDV system is expected to improve the accuracy and efficiency of diagnostic radiology and interventional radiology (IVR) procedures. In future, angiography system will equipped with a stereoscopic visualization interface that will provide a more flexible and more effective guidance tool for diagnostic radiology, especially for IVR that requires image-guided procedure.