This work presents a new approach for a wide analysis of the shape of breast tumors in ultrasound images. We have developed an environment for the filtering of the images, the segmentation of the nodules and the extraction of a series of measurements which describe the shape of the nodules. This will help in the computer-aided evaluation of the tumors and the distinction of benign and malignant nodules. The results extracted for the different features are coherent with the assessment of the specialists and represent a great help for the examination of the images and the decision making process.