A new method was used for the determination of lime potential of soils in the field.A flat-type glass pH electrode and a calcium-selective electrode were inserted into the thick soil paste,and the pH-0.5pCa value was found by measuring the potential difference directly with a portable mV-meter.It was found that the ranges of lime potential of various soils were:1.4-3.0 in yellow soils under natural forest;1.6-2.5 in laterites under monsoon forest;1.7-4.0 in laterites under rubber tree;1.8-2.5 in upland soils with shifting cultivation,3.2-5.5 in paddy soils.The lime potential in paddy soils was highest at the middle part of the soil profile,and that in other types of soil was lowest at a certain depth in the middle part of the soil profile.For a terra rossa.the lime potential was as high as 6.3-6.7.