A nonhuman primate model of tuberculosis that closely resembles human disease is urgently needed. We have evaluated the Philippine cynomolgus monkey, Macaca fasicularis, as a model of TB. Cynomolgus monkeys challenged intratracheally with extremely high doses of Mycobacterium tuberculosis (10(5) or 10(4) CFU) developed an acute, rapidly progressive, highly fatal multilobar pneumonia. However, monkeys challenged with moderate or low doses of M. tuberculosis (