Ⅰ. Soil moisture problems in the North China Plain and its associated areas were grouped into five categories according to the mode of soil moisture loss. Ⅱ. The diffusion theory does not account for the movement of moisture, under capillary forces, from free water into an uncompressed air-dry soil. Ⅲ. The rate of diffusion of moisture in soil samples from the heavy clayey horizons was correlated with penetration pressure of horizons. The rate of diffusion in horizontal soil columns was lower in samples from horizon or horizons with higher penetration pressure (kg/cm²). Ⅳ. The frequency of fluctuation of water table in heavy clayey profiles also bore certain relationship with the penetration pressure of the heavy clayey horizon or horizons in the Lower position of the profile.