There are several papers suggesting that colour-coded Doppler sonography is a useful diagnostic tool for the differentiation of malignant and benign lesions of the thyroid gland. This hypothesis (hypervascularization of malignant nodules) is reconsidered by preoperative examination of 65 patients by using colour-coded Doppler sonography and scintigraphy. Among these patients 21 carcinomas and 2 malignant lymphomas of the thyroid gland were found histologically. Colour-coded Doppler sonography was true positive in 10 cases, true negative in 28 cases, false positive in 14 cases and false negative in 13 cases. Our conclusion is that colour-coded Doppler sonography cannot be used unconditionally for the detection of carcinoma of the thyroid gland.