The occurrence of qualitative changes in meat was studied in a set of 1008 pigs slaughtered in four sanitation slaughter houses for the period of 12 months. PSE meat was found in 206 pigs (20.43 per cent) and DFD meat only in 9 pigs (0.89 percent) of the total number of pigs examined. The rule was applied that the defect should be demonstrated by two of three commonly used parameters (the pH value, colour and water loss by dripping). The highest occurrence of qualitative changes in meat of PSE type was registered in the group of animals with a defect of the respiratory organs (32.53 per cent) and the lowest in animals with diseases of sexual organs, including parturition complications (5.00 per cent). A similar trend was recorder even in the DFD meat occurrence. As to the seasons, the highest percentage of occurrence of PSE defects was in July and August (35.41 and 29.06 per cent) and the lowest (8.64 and 10.97 per cent) in March and January. The actual disease is proved to be only one of the secondary stress to induce the PSE meat formation.