The titer of antibodies to thyroglobulin (TgAb) was determined in 59 patients with diffuse toxic goiter before and in 21 patients 1.3 and 6 mos. after subtotal resection of the thyroid using the hemagglutination test (HAT), radioimmunoassay (RIA) and indirect immunofluorescence (IF). Microsomal antibodies were determined by the latter method only. Using the HAT TgAb were detected in 85% of the patients, using RIA and IF in 40 and 44%, respectively. A high titer of thyroid antibodies was detected on an average in 11-15% of the patients. Positive correlation was found in comparing the titer of thyroid antibodies with a degree of the expression of the thyroid lymphoid infiltration (TLI). It was most significant when it was between the titer of microsomal antibodies and TLI expression. The presence and severity of endocrine ophthalmopathy did not correlate with the TgAb titer. A tendency to the disappearance of TgAb or the reduction of their titer was noted in the first 6 mos. following operation.