Technical Abstract: The effect of temperature on pressure inactivation of hepatitis A virus (HAV) in Dulbecco’s modified Eagle media with 10% fetal bovine serum was studied at pressures of 300, 350, and 400 MPa and temperatures of -10, 0, 5, 10, 20, 30, 40, and 50C. Sample temperature at the time of pressure application strongly influenced the efficiency of HAV inactivation. Elevated temperature (>30C) enhanced pressure inactivation of HAV, while low temperature (below room temperature) was less effective in inactivating HAV. For example, a 1-min treatment with 400 MPa at -10, 20, and 50C reduced the titers of HAV by 1.0, 2.5, and 4.7 log x exp10 plaque forming units/ml, respectively. Pressure inactivation curves of HAV were obtained at 400 MPa and at three temperatures (-10, 20, and 50C). With increasing treatment times, all three temperatures showed a rapid initial drop in virus titer with a diminishing inactivation rate, or tailing effect, with increasing treatment time. This tailing was quite pronounced when HAV was exposed to 400 MPa at 50 C. For example, a treatment of 400 MPa for 30 sec at 50 C reduced the titer of HAV by 4.1 log x exp10; however, extending the treatment time to 10 min only increased reduction by an additional 0.8 log x exp10. Analysis of inactivation data indicates that the Weibull model consistently produced a better fit to inactivation curves than the linear model. Oscillatory high pressure processing on HAV inactivation was compared with continuous high pressure processing. Oscillatory high pressure processing for 2, 4, 6, and 8 cycles at 400 MPa and temperatures of 20 and 50 C did not considerably enhance pressure inactivation of HAV as compared with continuous high pressure application. These results indicate that HAV is unlike other viruses examined to date in that HAV has reduced sensitivity, rather than enhanced sensitivity, to high pressure at cooler temperatures. This work suggests that elevated temperatures are advantageous for pressure inactivation of HAV within foods.