To study the natural carrier of P. marneffei experiments were done in 16 Rhizomys pruinous senex, a species of bamboo rats trapped in various districts of Guangxi. The results of mycological cultivation demonstrated that the natural positive carrier rate of bamboo rats was 93.1%. Among the internal organs taken for culture, the lung had the highest positive rate, 87.5%; next in decreasing order was the liver (56.3%), spleen (56.3%) and mesentery lymph node (50%). Thus, it is reasonable to consider that bamboo rats are a reservoir host of P. marneffei. In this paper, the colony shape and microstructure of P. marneffei, isolated from bamboo rats, are described. A preliminary discussion is given on the epidemiological relations between bamboo rats and human Penicilliosis marneffei.