In this study, the effects of inositol addition on invertase secretion in Saccharomyces sp. W4 were examined. We found that invertase secretion in this strain was repressed when the completely synthetic medium lacking exogenous inositol contains more than 0.2% (w/v) glucose; however, when the yeast cells were grown in the same medium plus inositol, repression of invertase secretion in this strain occurred only at glucose concentrations higher than 2.0% (w/v). Furthermore, when sucrose was used as carbon source, increased invertase activity was observed in the presence of inositol. Repression occurred only at sucrose concentrations above 4.0% (w/v). More cell growth occurred and less residual reducing sugar was left in the inositol-containing medium than in the inositol-deficient medium as glucose or sucrose concentration was increased. These results demonstrate that inositol supplementation could derepress invertase secretion and cell growth in this yeast strain to some extent and sucrose was more suitable for invertase production than glucose. When the repressed yeast cells were transferred to the synthetic medium with low concentration glucose or sucrose, they could synthesize more extracellular invertase in the presence of inositol than in the absence of inositol.