The walls of mammalian arteries fluoresce with ultraviolet excitation in the wavelength range of 350–400 nm. We are using this property of natural fluorescence in conjunction with episcopic fluorescence microscopy, frozen section techniques, selective contrast enhancement, and a semi-automatic computer-based video analysis system to obtain dimensional data and 3-D coordinate maps of cerebral bifurcation geometry. The computer-video analysis system, comprised of commercially available video components, a Cromemco Z2D Computer, and electronic components built in our lab has a resolution of ± 1/256 mm at full-screen magnification. Our technique is based upon measurement of the video image of the block face during frozen sectioning of cerebral bifurcations. This technique allows us to obtain axially symmetric coordinate maps of cerebral bifurcation geometry without the use of block markers. In addition to mapping lumenal and adventitial surfaces the system can be used to map atheromatous lesions and the outline of the internal elastic lamina. Our initial geometrical data suggest a linear increase of 50–60% in cross-sectional area in the apical region and widening of the apical region in the plane of the daughter branches.