Abstract: Objective To propose a new method for content-based retrieval from medical CT image database on the basis of automatically extracted features of the images. Method An automatic feature extraction method is proposed based on expectation-maximization algorithm. A CT image is represented by a set of regions, each of which is characterized by a fuzzy regional feature vector reflecting the grey level, texture, shape, and the cumulative distribution histogram feature of the region of interest (ROI) to efficiently describe the difference between the ROIs. Results Compared with the submitted query image, the target images were retrieved in the order of similarity calculated by the proposed similarity measures. Conclusion The proposed technique for CT image retrieval is suitable for clinical application, with greater precision and efficiency for retrieval than the conventional methods.