Avian herpesviruses comprise a relatively large number of infectious agents, but only a few have been studied in detail, namely those that have a significant economic impact on poultry production. By far the most important members of this group of viruses in this respect are gallid herpesviruses 1 and 2 (GaHV-1 and GaHV-2). GaHV-1 is the etiological cause of an endemic upper airway infection of chickens, infectious laryngotracheitis, which is easily transmitted from animal to animal. GaHV-2, better known as Marek's disease virus, causes a peracute to chronic disease in chickens that classically presents with paralysis and widespread T-cell lymphoma, but is more recently characterized by neurological symptoms and rashes that are either transient or result in the acute and peracute death of affected animals. In this article, we discuss the characteristics of several avian herpesviruses and concentrate on the pathogenesis induced by those viruses and the control measures developed to combat two of the most important infectious diseases of domestic poultry worldwide.