for PTU because of minor side effects, mainly pruritus and rash. Their data were analyzed together with all other patients. Statistical Analysis.-Student's t test was used whenever appropriate. A total of 178 patients were treated with PTU, 55 of them for at least two courses. Four patients developed agranulocyto¬ sis, all of them while being treated with the drug for the second time. The rate of agranulocytosis was therefore 2.2% of all patients, and 7.3% of patients