It has been shown that dehydration markedly affects the activity of a number of enzymes connected with energy metabolism in the yeastSaccharomyces cerevisiae. Independently of the drying method used, there was found to be an inverse relationship between the activity of mitochondrial enzymes — NADH-dehydrogenase (EC 188.8.131.52), succinate dehydrogenase (EC 184.108.40.206) and cytochrome C oxidase (EC 220.127.116.11) - and the viability of yeast cells at the stationary growth phase. Dehydration led to an increase in activity only in exogenous NADH-dehydrogenase compared with activity in the initial compressed yeast. On the basis of alcohol dehydrogenase (EC 18.104.22.168) and catalase (EC 22.214.171.124) as examples, an ambivalent effect of the dehydration process on the activity of cytoplasmic enzymes has been demonstrated. The results obtained lead to the conclusion that the activity of individual electron-transport enzymes in yeastSaccharomyces cerevisiae is a sufficiently sensitive to be used as an indicator of the physiological state and to monitor a microbial biomass dehydration procedure.