Graft-versus-host disease (GVHD) is a serious complication of allogenic bone marrow transplantation. A descriptive study was conducted to determine oncology nurses' knowledge of GVHD in bone marrow transplant patients. The research question was: Do oncology nurses who participate in continuing education programs and read journal articles on GVHD have increased knowledge, as compared with oncology nurses who do not participate in these activities? Seventy-eight nurses completed a demographic data form and a GVHD questionnaire developed by the investigators (r = 0.71). Multiple regression analysis determined the relationships between independent and dependent variables. An analysis of variance determined a significant difference between the mean scores associated with the identified learning activities (F = 3.61, p less than 0.05). Continuing education activities and reading of journal articles were associated with higher knowledge scores (R2 = 0.1052, p less than 0.05). Many oncology nurses have no formal education in bone marrow transplantation and limited clinical experience with GVHD. Additional work must be done to determine if some oncology nurses practice from a weak theoretical framework and have limited rationales for their nursing actions. Further research, instrument development, and a teaching protocol on GVHD will enhance the nursing care needed by the patient with GVHD.