Porous glass films with immobilized solvatochromic dyes were investigated to develop an optochemical sensor for the determination of ethanol in water. Depending on the polarity of a solvent, i.e. content of ethanol in water, the immobilized indicators changed their fluorescence properties. Sensing films were prepared by immobilizing the dye with a sol-gel process. After preconditioning, these films were usable over a period of 5 weeks under continuous operation. The detection limit of ethanol in water was 0.6 vol.%, the response being linear in the range 0-50 vol.% ethanol. The response time was less than 5 min and the interaction with ethanol was reversible. The effect of pH and the temperature of the sample on the sensor properties were investigated.