Therapeutic trials using IFN, nucleoside analogs, or a combination of these two preparations have not provided encouragement for the treatment of CMV infections. The nature of the replicative cycle of CMV, as well as our inability to define processes specific for inhibition of viral replication, pose problems of significant magnitude at the present time. Furthermore, the need for early diagnosis and early intervention with a chemotherapeutic agent remain of paramount importance in the therapy of viral infection. Trifluorothymidine is active at low concentrations against CMV in vitro; but, our ability to use this drug in human disease remains to be established. Future therapeutic trials should take the form of combination chemotherapy or attempt to assess drugs acting at sites different in the replicative cycle than those currently available.