The effects of various carbon sources were examined to optimize the application of a novel foreign gene expression system in Saccharomyces cerevisiae using the upstream region of the isocitrate lyase gene (UPR-ICL) of Candida tropicalis. A UPR-ICL-LacZ fusion gene was transformed into S. cerevisiae to compare the gene expression levels by measuring the beta-galactosidase activity. Glucose, acetate, glycerol, lactate, and ethanol were used as carbon sources in different minimal media. All the carbon sources except for glucose led to a rapid increase in enzyme activity. Judging from the productivity and specific activity, acetate was the most effective carbon source for gene expression in the minimal media. At the same time, a high level of enzyme activity was also obtained in cells grown on glucose to later growth phases. This phenomenon was also observed in cells at the stationary phase in a rich glucose medium, and the productivity per unit volume of broth was the highest out of all the conditions examined. Determination of the glucose and ethanol concentrations in the media revealed that the increase in the level of gene expression promoted by UPR-ICL in S. cerevisiae was primarily dependent on glucose starvation, but not necessarily on ethanol accumulation, during cultivation. That is, gene expression is repressed until the stationary phase, where glucose is exhausted and the Sell density becomes high. Immediately after glucose exhaustion, high levels of protein production were obtained. Accordingly, for rapid production of target proteins at high levels using this system on a laboratory scale, transferring cells cultivated in a glucose medium to a minimal acetate or ethanol medium seems effective.