For quantitative evaluation of human TV nailfold capillary microscopy a new semi-automated image-analyzing system called "CapiShape" is presented. Skeletons and boundaries of capillaries are obtained by a special image processing algorithm to describe the shape of capillaries. In addition to conventional parameters such as diameters and loop widths for the size of single capillaries, new non-size parameters related to surface area and the skeletons are calculated. To describe capillary distribution in a nailfold, the ratio of distance between capillaries to its projection in the X axis, and area percentage are indicated. With different operators and different orientations of the camera, the measured differences in diameters and loop widths are smaller than 1.5 microm, and in area percentage smaller than 1.0%. As practical examples, applications of CapiShape to patients with scleroderma showed marked, significant differences in capillary size between patients and controls, patients with diabetes differed significantly in non-size parameters from controls. CapiShape is specially designed for clinical applications, and besides the usual measures new parameters for describing nailfold images may be developed. CapiShape is safe and easy to use for diagnosis, routine examination, and quantitative follow-up studies.