One-dimensional structural localization on a scale approximating the sizes of the structures themselves is accomplished for polarized tissue by a new microcomputer-based stereological method The tissue of interest is the inner rat aortic wall, viewed by transmission electron microscopy. Particular attention is given to the interface between intima and media. Locational analysis of smooth muscle cells, elastin, collagen and other structures near this interface can be performed. The key to accomplishing the analysis within a reasonable time rests with a microcomputer program which simultaneously records structure codes from the microcomputer keyboard and X,Y-coordinates from an electronic digitizing board. The stereological solution to this problem is applicable to a wide range of situations with polarized geometries.