The authors describe the ecology of attacks by vampire bats and the epidemiology of rabies (paralytic rabies) transmitted by these bats in Argentina, based on data obtained from an epidemiological vigilance programme conducted between 1984 and 1993. It was found that rabies spread rapidly among vampire bats, causing high mortality (over 50%); subsequently, the population recovered slowly due to the low reproductive rate. This explains the features of paralytic rabies, such as high mortality among affected populations, brief duration and subsequent recurrence. Paralytic rabies occurs throughout the year without evidence of seasonal occurrence and with no relationship to rainfall. This is because vampire bats remain active within their habitat, neither hibernating nor migrating. The problem created by vampire bats depends on the ecosystem of their habitat. In the livestock ecosystem, the bats are synanthropic and their population is abundant. They feed almost exclusively on livestock and attacks on human beings are sporadic. In this ecosystem, paralytic rabies is a serious economic problem because of its frequency and readiness to spread (41 separate outbreaks were recorded in addition to an epidemic). On the contrary, in the scarcely populated livestock ecosystem, the vampire but population is much smaller; they feed on various species of animals, and attacks on human beings are more common, but paralytic rabies occurs only sporadically (one isolated outbreak). For overall control of paralytic rabies, the authors recommend reduction of the vampire bat population to a safe level, in order to break the chain of rabies transmission and diminish attacks by bats.