To assess the differential points of benign and malignant lesions, authors evaluated the sonographic findings of 45cases o fthyroid nodules, comprising 31 cases of benign nodules and 14 cases of malignant nodules. Sonographic findings were evaluated in terms of the echo patterns, margin, size and multiplicity of the thyroid nodules. There is no siginificant differences between the benign and malignant nodules in echo patterns and multilicity. Alarge(more than 4 cm in diameter) and clear marginated nodule is suggestive of benignancy. Differentiation of benign from malignant thyroid nodules on the basis of sonographic findings seems to be difficult.