Methodical questions of monitoring of water status in soil, cereals grain and wood are discussed (where monitoring is understood as registration of time and spatial variability of selected properties). Amount of variables which is necessary in order to determine water status depends on the complexion of the considered phenomena and is, so far, the matter of arbitrary choice. In most practical cases the water status is expressed only by moisture of the considered material (like the building timber). In practical terms, two variables suffice to express water status in cereal grain: moisture and temperature. To describe water status in the soil not less than five variables are needed: amount of water (the soil moisture), soil water potential, salinity, oxygenation and temperature. The only sensors that can be integrated in modern data acquisition systems must be read electrically. Therefore electroresistance and electrocapacitance methods were considered. Dielectric sensors were recognized as the proper choice. Soil is a complex material having instable characteristics. For this reason it is the most difficult task to monitor soil water status, particularly to determine the soil moisture . Therefore it has been assumed that measuring methods verified for the soil will be also suitable for other, less complex materials. Thus , monitoring of soil water status was mainly discussed. Special attention was focused to the time domain reflectometry, TDR, as the semiselective method for the soil moisture and salinity determination.