Immunohemolytic anemia secondary to methyldopa therapy occurred in an adult. Folate deficiency was also present because of rapid red blood cell turnover induced by the hemolysis. The globulin responsible for the positive direct and indirect Coomb's tests was of the warmacting IgG variety, with specificity for the Rh locus. The degree of hemolysis decreased and the hematocrit reading increased when methyldopa therapy was discontinued and prednisone and folate sodium were given. The Coomb's tests remained positive nine months after treatment was begun.