Physiological effects of deficiency of pantothenate, a necessary precursor in the synthesis of coenzyme A, were studied using the yeast strain Saccharomyces cerevisiae CBS 8066. Cells were grown on defined media in anaerobic batch cultures with glucose (50 g/l) as the carbon and energy source. Batch cultures containing more than 60 mu g/l pantothenate showed no significant differences with respect to growth rates and product yields. However, with an initial pantothenate concentration of 30 mu g/l, the average glucose consumption rate was 50% lower than in rich medium and, at even lower concentrations of pantothenate, the culture did not consume all the glucose in the medium. Furthermore, pantothenate deficiency caused the acetate and pyruvate yields to increase and the biomass yield to decrease, compared to the yields in pantothenate-rich medium. The increased acetate formation could be counteracted by initial addition of acetate to the medium, and thereby the glycerol yield could be decreased. An initial addition of acetate of 1.6 g/l to pantothenate-deficient medium (30 mu g/l) caused a 35% decrease in glycerol yield and a 6% increase in ethanol yield. Furthermore, the time required for complete conversion of the glucose decreased by 40%. Acetate addition affected the acetate and glycerol yields in a similar way in pantothenate-rich medium (1000 mu g/l) also.