Fundamental thermal properties of various high water content materials were determined using a number of thermal testing methods. Tests were conducted on peat soils, solid wastes, industrial sludge, and bentonite slurries. Thermal conductivity, heat capacity, and thermal diffusivity were determined. The thermal conductivity of the materials was determined using a needle probe method. The volumetric heat capacity of the materials was determined using a dual probe method. These values were used together to obtain thermal diffusivity. Analytical methods are also used to determine heat capacity and thermal diffusivity. The theory for determination of thermal parameters using the various methods is presented. Experimental methods were determined to be effective at measuring thermal properties of high water content materials. Thermal parameters are dependent on material composition and structure. Heat capacity and thermal diffusivity are greatly affected by water content because of the high heat capacity of water compared with air and solids. A comparison is made between experimental and analytical methods used to determine thermal parameters. Good agreement was observed between experimental and analytical methods. Results of thermal tests have applications in the prediction of heat transfer through soils, sludges, and wastes.