The parameters in the cultivation of ergosterol were studied. The relationship between biomass, ergosterol content of Saccharomyces cerevisiae and parameters such as dissolved oxygen (DO), oxygen uptake rate (OUR), pH, glucose concentration were discussed. The constant feed rate fed-batch, constant glucose-concentration fed-batch, exponential fed-batch, DO-control exponential fed-batch, pulse fed-batch and DO-control pulse fed-batch are used to optimize the ergosterol fermentation. It was found that DO could serve as an effective control parameter for yeast fed-batch fermentation. When the DO was kept at 12% ( +/-1%) and pulse fed-batch was used, the total ergosterol yield could be enhanced to 1160 mg/l. (C) 2003 Elsevier Inc. All rights reserved.