In comparison to older children and adults, neonates are immunologically incompetent. They are susceptible to infections caused by a variety of microorganisms, including bacteria, fungi and viruses. These infectious agents may be acquired by neonates either prenatally, during the intrapartum period or postnatally. The purpose of this review is to emphasize the potential impact of viral infections contracted by neonates at the time of delivery or within the neonatal period. The viruses reviewed include the herpes group of viruses (cytomegalovirus, herpes simplex viruses and varicella-zoster virus), type B hepatitis virus, human immunodeficiency virus, respiratory viruses, enteroviruses, rotavirus and human papilloma virus. For each virus the potential sources and incidence of the infection, the common manifestations of the illness, and possible means of prevention and therapy are discussed. Although infections caused by bacteria tend to be more clinically dramatic and more immediately life-threatening, it is emphasized that infections caused by viruses are common and associated with substantial long-term morbidity. Perinatal viral infections need to be recognized as early in life as possible so that their natural history can be more completely defined and any possible intervention made.