In their comment, Sobel and Glick stated that the fact we were able to accumulate three patients with agranulocytosis in 1 year is somewhat surprising. We treated 1356 patients with Graves' disease while our granulocyte colony—stimulating factor study was carried out from July 1990 to August 1991. The incidence of antithyroid drug-induced agranulocytosis (granulocyte count, 9 /L) was 0.4% (six of 1356), which was the same as that (0.2% to 0.5%) reported previously. 1 Noguchi Thyroid Clinic (Beppu, Japan) is a special hospital for thyroid disease. About 1200 patients with Graves' disease per year visited this clinic from western Japan. As reported in our article, 2 from 1975 to 1987, 15 398 patients with Graves' disease were treated with an antithyroid drug in the Noguchi Thyroid Clinic. Of these, 55 (0.4%) were found to have agranulocytosis. We do not think that there is a discrepancy between our data and