The recent profusion of antiviral research has resulted in significant advances toward prevention and treatment of herpes group virus infections. The most promising new agent is acyclovir, which is available in topical, intravenous, and oral formulations. Results of clinical trials of acyclovir for prevention and treatment of herpes simplex, varicella-zoster virus, cytomegalovirus, and Epstein-Barr virus infections are discussed, and the potential problem of antiviral resistance considered. Vidarabine therapy is reviewed briefly, and future new drugs with activity against herpesviruses are mentioned.