To the Editor:— Since the report by Cahal 1 of nine cases of hemolytic anemia in patients treated with methyldopa, we have studied patients taking this hypotensive agent to determine the frequency of occurrence of positive Coombs' tests and hemolytic anemia. Carstairs et al 2 studied two patients with hemolytic anemia who had been taking methyldopa for 15 months. They also did a survey on patients attending their hypertensive clinic to determine the incidence of patients having a positive Coombs' test while on a regimen of antihypertensive therapy. They investigated 104 patients, 57 of whom were taking methyldopa (Aldomet), and 47 who were taking other hypotensive drugs. Of the 57 taking methyldopa, five had a positive Coombs' test, whereas none of the other 47 patients did. The difference between these two groups is statistically significant. However, none of the patients in this survey became anemic; all had been receiving methyldopa