The aim of the work was determination of the effect of raw material quality on the course and final effect of ethanol fermentation of maize mash using cultured and rehydrated distillery yeast Saccharomyces cerevisia Safethanol 3035 The material for investigation was maize grain of Kosmo 230 cultivar: fresh (immediately after harvest), dried or stored without preservation (8 and 19 months, 20ºC). Maize grain stored for 8 months was infected with Fusarium fungi in 100%. After 19 months of grain storage the amount of Fusarium spp. isolates decreased but the amount of Penicillium spp. increased. The process of fermentation of maize dried or stored for 19 months was over after ca. 2 days. The mashes of fresh corn or stored for 8 months need ca. 3 days to complete the fermentation. The degree of carbohydrates consumption was very high, over 99% in all samples. Physiological condition of yeast after fermentation of lower quality material was significantly worse than in control samples. The yield of ethanol fermentation of poor quality grain were slightly worse than in case of fresh or dried grain, but the differences were not significant, which confirms the suitability of this raw material for fuel production purposes.