The inactivation kinetics of two yeasts, Saccharomyces cerevisiae CCRC 20271 and Zygosaccharomyces rouxii CCRC 21873, were determined at combinations of different hydrostatic pressures (0.1-300 MPa) and temperatures (35-55 degrees C). First order kinetics were applicable to both yeasts under the conditions used, except that slight deviations occurred for Z. rouxii at combinations of 35-40 degrees C and 150-300 MPa. At pressures of 0.1 to 100 MPa S. cerevisiae was more resistant to heat and also to pressure than Z. rouxii. The Arrhenius plots of the specific death rates for both yeasts at various pressures showed similar yet distinct patterns. The average activation energy (E(a)) for Z. rouxii was about 1.51 +/- 0.08 x 10(5) J/mol and was apparently independent of pressure, however, E(a) values of S. cerevisiae were roughly divided into two groups of parallel lines, one obtained at pressures of 0.1-100 MPa was 1.65+/-0.61 x 10(4) J/mol, the other was 1.23 +/- 0.17 x 10(5) J/mol at 150-300 MPa. Consequently, the combined effect of pressure and temperature on the survival of the yeasts appeared to be additive, but this effect tended to increase stepwise for S. cerevisiae as the pressure increased.