The average volumetric intracellular concentrations of acetophenone and phenethyl alcohol were determined during the bioreduction of acetophenone using resting cells of Saccharomyces cerevisiae in aqueous solutions at 30 degrees C. The behavior of their distribution coefficients (ratio of intracellular to extracellular concentrations) during the bioreduction process was evaluated with different cell preparation and extracellular conditions. The distribution coefficient of acetophenone was found to be in the range of 2.3-4.0. The distribution coefficient of phenethyl alcohol was found to be in the range of 1.3-1.8. Both the distribution coefficients were correlated significantly only with the physiological state of the resting cells as reflected by the relative cell mass (0.65-1.09). The correlation is approximately linear with the largest slope for the toxic reagent, acetophenone. No significant effects on the distribution coefficients were experimentally observed or were present in a regression analysis for the concentrations of acetophenone (0-0.30% v/v), phenethyl alcohol (0-0.20% v/v), ethanol (1.60-2.25% v/v), the extracellular pH (pH 2-7), or the presence of the salts: KCl, KH2PO4, MgSO4 NaCl, and CaCl2 teach 0-0.1 M in the medium. Different cell initialization times (0-6 days) and initialization conditions were also included.