Immunotherapy has not only become the accepted standard for some CMV infections, but also remains an area of active investigation for the treatment and prophylaxis of CMV infections. Polyclonal immunoglobulin administration has improved the survival of CMV pneumonitis in BMT recipients, and monoclonal anti-CMV antibodies, notably MSL-109, appear to increase the time to relapse of CMV retinitis in patients with AIDS. The adoptive transfer of CMV-specific CD8 cells is under investigation as another CMV prophylactic strategy in BMT recipients, and it is hopeful that this methodology can be applied to the therapy of established CMV infections.