ABSTRACT The incidence of asymmetrical thyroid scans as measured by hand scanning over the thyroid with a Geiger Muller tube has been investigated in 32 patients with Hashimoto's disease in whom the thyroid gland was hard or nodular or in whom cancer was suspected clinically. In 19 of 32 patients the thyroid scanned asymmetrically. No patient in the series was shown to have thyroid cancer. It is suggested that an asymmetrical scan is of no value in the differentiation of Hashimoto's disease from thyroid neoplasm.