A two-dimensional sonoelastographic technique called "disparity mapping" was applied to breast sonographic examinations in eight patients to test discrimination between benign and malignant lesions. With probe compression, pairs of gray-scale sonographic scans were obtained about 1 second apart. The disparity mapping procedure calculated the apparent displacement of the speckle pattern about each point in the image and presented that information in the form of a disparity map. Findings were consistent with a firm lesion in two of the three cancers, were indistinguishable from normal tissue in all three fibroadenomas, were indistinguishable from normal findings in one cyst, and showed no disparity in one cyst because it had few internal echoes.