Patients with steroid-resistant acute graft versus host disease (aGVHD) have a dismal prognosis, with mortality rates in excess of 90%. We sought to identify a subgroup of patients less likely to benefit from initial therapy with corticosteroids as well as the impact of response on day 14 on outcome. Retrospective evaluation was performed of patients with biopsy-proven aGVHD treated with corticosteroids after allogeneic HSCT at M.D. Anderson Cancer Center from 1998 through 2002 (N = 287). Overall response to first-line therapy on day 14 was 56%. Grade III-IV aGVHD and hyperacute GVHD were the most significant factors predicting failure. Patients who fail to respond to steroids by day 14 should be considered for clinical trials. Severity of aGVHD, hyperacute GVHD, and sex mismatch could be integrated into prognostic scoring systems which may allow for pretreatment identification of patients unlikely to benefit from standard therapy with corticosteroids.