ABSTRACT: Application and interpretation of longitudinal profile measurement of specific electric conductivity (resistivimetry) and water temperature (thermometry) along karstic underground stream in the cave are presented on the example of Gombasecká cave in the Slovenský kras Mts. Measurements of underground river water temperature and specific electric conductivity were performed there on Oct. 15, 2009, with the step of 1.0 meter in the streamline of active flow or (if wider than 1.0 meter), along its left and right side, 20 cm aside the stream-bank. Results of such measurements can be used especially for identification of hidden tributaries into the main stream, but also can help us to decide on the water communication with the surface. This simple, but very sensitive method can be also helpful in stream hydrodynamics description within the karst system. This paper documents probably the first use of such a method in the cave environment.