The influence of oxygen supply rate on the growth and the production of both ethanol and acetaldehyde by the aerotolerant fermentative bacterium Z. mobilis is discussed in this work. The results showed similar values of cell mass yield (0.043 g/g) for the five different levels of initial volumetric oxygen transfer coefficient (KLa) studied. The maximum specific growth rate (µx,m.) under anaerobic conditions was higher than those found in aerated runs. Anaerobic cultivation resulted in the best ethanol yield (0.38 g/g). For initial KLa values of 62, 94, and 118 h-1, ethanol yields were 0.10, 0.12, and 0.09 g/g, respectively, whereas for KLa of 30 h-1, an intermediate value (0.24 g/g) was achieved. Under anaerobiosis, no acetaldehyde was produced. With initial KLa values of 62, 94, and 118 h-1, acetaldehyde yields were similar (0.12 to 0.17 g/g), and for KLa of 30 h-1 only 0.07 gram of acetaldehyde was formed per gram of glucose. Although increasing values for the maximal specific acetaldehyde formation rate were calculated as KLa was increased, our results showed that the presence of an excess of dissolved oxygen throughout fermentation is enough to provide appropriate conditions for the production of acetaldehyde by Z. mobilis.