The paper discusses the analysis of ethanol (E85) fuel atomization generated by piezoelectric fuel injectors operating in a high-pressure gasoline direct injection system. The methodology and tests results of the influence of the fuel (E85) injection pressure and combustion chamber back pressure on the changes of the fuel spray geometrical parameters during the injection and on the values characterizing the injection quality have been presented in the paper. The tests were performed for one value of the air backpressure (1.5 MPa; as in modern supercharged DI engines) at the injection pressures of 5 and 20 MPa. The following comparative indexes were analyzed: linear and radial spray penetration during the injection and the velocity of the spray propagation.The investigation consisted in a visual recording of the process of fuel (ethanol E85) injection realized into a high pressure chamber. The recording was carried out with a high speed camera (High Speed Star 5 by LaVision) fitted with a CMOS monochromatic image converter. The speed of filming was limited to 10,000 frames per second (time resolution 100 μs) in order to maintain the required spatial resolution of the performed image analysis (512x512 pixels; pixel size 17x17 μm). For the processing and analysis of the recorded images the authors used DaVis and Command Language by LaVision.The analysis of the recorded images allowed a determination of the influence of the injection pressure on the geometrical parameters of the spray, uniformity of the injection and fuel atomization. The assessment of the radial speed of the spray propagation was performed with a resolution of 1° on the whole circumference from the front of the spray cone to the injection nozzle. This allowed determining of the level of unevenness of the radial spray penetration during the injection depending on the injection parameters.