Observation of the ultrastructural and intracellular chemical changes of CaCl2-tolerant strains is important both for understanding their adaptation mechanism under high salt stress and for providing theoretical basis of their application in treating high-CaCl2 wastewaters. A novel strain V 430 isolated by us has been successfully used to decrease the chemical oxygen demand (COD) concentration of diosgenin wastewater from 20 g l(-1) to less than 0.5 g l-1. For this study, strain V430 was incubated in culture media of different CaCl2 concentrations (up to 9.0%). Strain V430 cells incubated in media of high CaCl2 concentration excreted extracellular substances and accumulated intracellular Ca2+ and K+ and free amino acids. The levels of intracellular cations and free amino acids increased with increase in CaCl2 concentration of the medium. The increase in total free amino acids was mostly due to accumulation of glutamic acid. The strain cells under 9.0% CaCl2 stress took up K+ in a short time, while accumulation of Ca2+ proceeded over the whole growth process.