To evaluate the efficacy of myocardial T2 values in the assessment of allograft rejection, we performed magnetic resonance (MR) imaging at 0.5 T serially in seven cardiac transplant recipients and singly in seven normal volunteers. Cardiac-gated multi-echo spin echo images were obtained; T2 values were estimated by a two-point method from regions of interest in the myocardium. Patients underwent MR and cardiac biopsy at various times after transplantation. Forty-two patient exams were performed. All biopsies showed either no rejection or early stages of rejection: grade 0 in 8 examinations, grade 1 in 28, and grade 2 in 6. Myocardial T2 values in patients in early stages of cardiac rejection were slightly higher (but not statistically significant) than those in non-rejecting patients and normal volunteers. Although this study did not allow prospective detection of cardiac rejection in our patient group, it demonstrated a trend toward higher T2 values at higher biopsy grades that may indicate an ability to assess more severe stages of transplant rejection.