The batch, fed-batch and continuous cultivation of Pachysolen tannophilus on various substrates (xylose, glucose, glucose/xylose and hydrolysate of cellulose/hemicellulose) was performed under aerobic, microaerobic and anaerobic conditions in stirred tank reactors equipped with pH-, redox potential-meter, microfluorometer, off-gas analyser, and for continuous cultivations with crossflow filter. The concentrations of ethanol, acetaldehyde, acetate, glucose, xylose, xylitol and the activities of the intracellular enzymes alcohol dehydrogenase, NADH-dependent xylose dehydrogenase, NADPH-dependent xylose reductase, NAD(+)-dependent xlitol reductase and NADP(+)-dependent xylitol dehydrogenase were determined as a function of the cultivation time. Under anaerobic conditions mainly cell mass and a low amount of ethanol were formed. The highest ethanol productivity was obtained under microaerobic conditions. Under anaerobic conditions xylitol was the main product. Glucose and xylose were consumed consecutively. Steady state operation of an integrated system consisting of a cellulose/hemicellulose enzymic hydrolyser reactor and a fermenter for glucose/xylose conversion to ethanol was maintained. However, the ethanol productivity was low due to the low sugar concentration, which was necessary because of the inhibition of the hydrolyses caused by high sugar concentration.