Under the title "Inveterate foci of plague in Brazil", the authors describe a recent outbreak of this disease in Nova Friburgo in the border of Teresopolis District (Rio de Janeiro State) where similar outbreaks had occurred in 1941, 1952 and 1960. After a short review on the situation of plague in Brazil, they stress the problem of chronic foci - apparently isolated and without connection between them - but with unpredict reccurrent outbreaks. Although these foci seem to be circunscribed the authors believe that under pressure or "ecologic stimulus" an "adaptative radiation" to neighbourhood could happen, but always within the same physiographical area.