Venezuelan hemorrhagic fever (VHF) is a severe disease characterised by fever, malaise, sore throat, followed by abdominal pain, diarrhea, a variety of hemorrhagic manifestations and convulsions. The arenavirus Guanarito is the causal agent and the virus natural reservoir is the rodent Zygodontomys brevauda (cane mouse). The disease affect agricultural male workers, between 14-54 years of age, mainly from Guanarito municipality of Portuguesa state and adjacent regions of Barinas State. Since VHF emergency in 1989 up till 1997, 220 cases have been reported with a fatality rate of 33%. Epidemiological informations suggest that VHF has a cyclic behaviour, with epidemic periods of high incidence, every 4-5 years. During the interepidemic periods few VHF cases are reported.