The objective of the present study was to determine changes in the properties of myofibrillar proteins in PSE pork meat treated using ultrasounds and stored for 96 hours. The raw material studied was pork meat (m. biceps femoris) chilled for 24 hours at 7 °C; its colour was pale and its pH₂₄ was ≤5.6. The pork meat investigated was delivered from a slaughterhouse, 24 hrs after slaughter. The muscle was divided into three parts of a similar weight. One part constituted a control sample (CS), the other two were treated by ultrasounds of a frequency of 25 kHz (sample US) and 45 kHz (sample ZS), respectively. The intensity of ultrasound waves was 2 W·cm^-2. The exposition time in the ultrasound field was 2 minutes. The meat samples were stored under the chilling conditions. After the storage lasting: 24, 48, 72, and 96 hours after slaughter, the myofibrillar fragmentation index (MFI) of and a total content of –SH reactive groups in the meat samples were measured, whereas cooking losses and water binding ability of myofibrillarar gels were measured 24, 48, and 72 hours after slaughter. It was found that the sonication of meat using 25 kHz ultrasounds caused a change in the direction of the post mortem biochemical metabolism of the meat proteins, and the result of those changes was the increase in the content of -SH reactive groups. When the meat was treated by 45 kHz ultrasounds, no significant differences were found in the content level of -SH reactive groups and in the MFI compared to the control sample of meat. Furthermore, there was found no effect of the sonification of meat on the cooking losses in and water binding ability of the gelated meat homogenates. A positive correlation was found between the content of –SH reactive groups and the cooking losses in the samples treated by ultrasounds; MFI and water binding ability were positively correlated in the gelated homogenates of the control sample and the sample (ZS) sonicated by 45kHz waves. A negative correlation exists between the content of -SH reactive groups in it and water binding ability of the control sample, in the ZS sample: between MFI and the cooking losses in it.