Competitive inhibition of interleukin 2-dependent lymphocytes by daclizumab demonstrates some beneficial effects in the treatment of graft-versus-host disease (GVHD). Sixteen patients with steroid refractory GVHD received daclizumab (1 mg/kg BW) on d 1, 2 (−5), 7, 14 and 21. Twelve patients suffered from grade III–IV acute GVHD and four patients from extensive chronic GVHD. Responses were observed in nine patients (six acute, three chronic GVHD). Fourteen out of 16 patients acquired infections during daclizumab treatment and three deaths were infection related. Daclizumab demonstrates limited activity and is associated with an increased incidence of infectious complications.