Optimum conditions were determined for the growth of Burkholderia pseudomallei in natural soils or waters. It grows better in paddy soil, crop-covered and fallow field than in fresh and salty water. Although the optimal temperature and pH for the growth were 37 or 42°C, and 6.5 or 7.5 in an environmental-mimicking soil medium, this bacterium can still grow at 4°C, which was suggested to be related with the occurrence of melioidosis in some cold areas. In soil media with water content <15. B. pseudomallei did not grow until 60 d of incubation, suggesting that water contents of soils in which it dwelled would be one important factor in determining the growth rate.