ABSTRACT: Hydro-geological investigation forms an integral part of the exploration of the Gbely lignite deposit. From initial investigatory stages, hydro-geological work concentrated on verifying the precise back and bottom of this seam. This work was mainly based on experience gained from the excavation, preparation and extraction of lignite deposits in the Hodonín South-Moravian Mine, situated in the Vienna Basin. Preliminary influx prevention during extended driving there was established when both mining and geological and hydrological investigation began in 1978, and safety regulations against sudden inrushes of water and water-bearing deposits were processed in the IVth mining section in 1990. Since 1997, influx prevention for excavation, preparation and extraction in mining sections No. III, V, VIII, IX, X, XI and XII. have come into force.