Fifty patients who had a palpable soft-tissue mass and an apparently normal radiograph were studied with ultrasound imaging before excision or biopsy of the lesion was done. As shown by the sonograms, thirty-five lesions had a discrete echo pattern (usually reduced echoes and a clearly defined lesional margin) and fifteen had an ill defined pattern (similar to the pattern of the surrounding normal tissues with no definable lesional margin). Fourteen lesions were malignant and thirty-six, benign. The sonograms of all fourteen malignant lesions showed a discrete pattern, while the sonograms of the benign ones showed twenty-one discrete and fifteen ill defined patterns. Therefore, the malignant lesions produced a discrete pattern in every instance, and every lesion that produced an ill defined pattern was benign. Fourteen of the fifty lesions were cystic; of these, thirteen were benign and one was malignant. The sonograms correctly identified the cyst in seven of the thirteen benign lesions and in the one malignant cystic lesion. Based on these findings, we concluded that all palpable soft-tissue masses that appear to be discrete on a sonogram should be diagnosed without delay by examination of a specimen taken at biopsy, whereas lesions that have an ill defined appearance on a sonogram may be assumed to be benign and may safely be observed in selected patients.