Graft-versus-host disease can develop in immunosuppressed individuals who receive blood product transfusions that contain imrnunocompetent lymphocytes. We report a case of transfusion-associated graft-versus-host disease(TA-GVHD) that developed in a patient with acute lymphocytic leukemia who were undergoing therapy. The groups at risk for development of TA-GVHD, the clinical presentation and course, and methods of diagnosis are summarized. Prevention of TA-CVHD is possible by irradiation of blood products given to patients at risk, but problems remain in determining the groups that warrant such measures. We should be aware of the risk of developing TA-GVHD after routine blood transfusion, especially in areas where the population's HLA types are rather homogeneous. (Kor J Dermatol 1996;34(2): 345-349)