The lethal effects of shock pressure treatment on suspended Vibrio sp. cells were examined. Lethality of shock pressures to the Vibrio sp. cells increased with the increase in the values of maximum shock pressures generated in the cell suspension. When the value was around 114 MPa, the total number of colony-forming cells was reduced from 10(8.5+/-0.1) colony-forming units (CFU) to 10(3.3) - 10(3.4) CFU/ml, and complete loss of colony-forming ability was seen at the maximum value of 282 MPa. Almost all the cells could survive after the exposure to shock pressures including the maximum value of around 189 MPa in the presence of 2% sodium ascorbate (VitC-Na), whereas the total number of colony-forming cells was reduced to 10(1.6)-10(2.1) CFU/ml in the absence of VitC-Na. The surviving cells, however, showed sensitivity to 0.8% sodium cholate, a strong detergent. About 11% of cell-associated proteins had leaked out when the cells were exposed to lethal shock pressures including the maximum value of around 290 MPa in the absence of VitC-Na. These results indicate that the radicals generated in the cell suspension may be closely related to the loss of colony-forming ability of the Vibrio sp. cells. Damage to the outer membrane structure also seems to have occurred by the exposure to shock pressures.