A critical step for a successful conservation of endangered species is the correct diagnosis why the species of interest is decline. A failure of diagnosis what is wrong is at the heart of much unsuccessful conservation. The research assessed changes of population size of banteng between 2002 and 2006 and discussed the role of predation by dholes on the decline of banteng in Baluran National Park. Concentration counts in 13 waterholes in 2002 and in 11 waterholes in 2006 were conducted to monitor the population change. Observations of predation on banteng by dholes were done through series of observations from April to July 2002 and from March to July 2003 in the feeding ground of 350 ha in Bekol. Disproportional number of young banteng and change of sex ratio in population in 2002 indicated a possible decrease of the population. During four years, the number of animal diminished from 126 to only 15 banteng. An estimate of rate per capita of population growth (r) was -0.53 yearG1. The data suggested that high predation rate by dholes was the responsible factor of population decline. However, an action to reduce dholes in BNP was an agony of choice, because both banteng and dhole were classified as endangered species. A reduction of pack size of dholes was the best remaining options to prevent banteng from extinction. If the pack size of dholes was small enough, they would switch to prey the smaller animals.