The shape and size characterization of two types of potassium titanate fibers respectively prepared from anatase by the traditional calcination and from TiO2 . nH(2)O by the promoted calcination were characterized by image analysis, showing distinguished advantages in description and comparison of shape of one dimensional materials. The accurate and quantitative relation of pixels of a digitized image to corresponding true size and the specifications, as well as the magnification of the image analysis system, and the horizontal resolving power and the scanning area of video-camera, of devices of the image analysis system, were found, which avoids the measuring deviation occurred in getting the relation between the pixels of a digitized image and corresponding true size from the digitized calibration graticule image in previous researches. Proposed image analysis parameters for characterizing shape and size of fibers were the length, the diameter, and the ratio of length to diameter, expressed by L-L, L-D, and L-L/L-D, respectively. Fibers are defined those particles with L-L/L-D > 3 for calculating the fiber content of a complex particle system. The non-fibrous particles were characterized using equivalent projected area diameter and the shape factor. The sampling method and the image analysis method proposed in the present study are generalized methods that can be applied for other fiber systems. (C) 2004 Kluwer Academic Publishers.