Plague in man occurred from 1968 to 1970 in mountain villages of the Boyolali Regency in Central Java. Infected fleas, infected rats, and seropositive rats were collected in villages with human plague cases. Subsequent isolations of Yersinia pestis and seropositive rodents, detected during investigations of rodent plague undertaken by the Government of Indonesia and the WHO, attested to the persistence of plague in the region from 1972 to 1974.Since 1968, the incidence of both rodent and human plague has been greatest from December to May at elevations over 1000 m. Isolations of Y. pestis were obtained from the fleas Xenopsylla cheopis and Stivalius cognatus and the rats Rattus rattus diardii and R. exulans ephippium. The major risk to man has been fleas infected with Y. pestis of unique electrophoretic phenotype. Infected fleas were collected most often in houses.Introduced in 1920, rodent plague had persisted in the Boyolali Regency for at least 54 years. The recent data support specific requirements for continued plague surveillance.