Accurate minutiae extraction from fingerprint images is heavily dependent on the quality of the fingerprint images. In order to improve the performance of the system, much effort has been made on the image enhancement algorithms. If the preprocessing is adaptive to the fingerprint image characteristics in the image enhancement step, the performance gets to be more robust. In this paper, we propose an adaptive preprocessing method, which extracts five features from the fingerprint images, analyzes image quality with clustering method, and enhances the images according to their characteristics. Experimental results indicate that the proposed method improves the performance of the fingerprint identification significantly. q 2005 Elsevier B.V. All rights reserved.