Changes occurring in the hydration of meat during post mortem ageing have a significant influence on its quality traits, especially tenderness. The aim of the study was to determine relationships between the structural changes taking place in meat during the ageing process and its water holding properties. The studies were carried out on SM muscles removed from the carcasses of young slaughter cattle of Black and White lowland breed 1.5 hours after slaughter. Muscles were packed and aged for 72 hours at 4°C. This was followed by morphological and physicochemical examinations. The microstructural changes in meat were studied using an electron microscope. Water holding capacity was examined by means of centrifugal method. The ability of the tissue to hold native water was estimated by filter paper press method. The studies were conducted 4, 24, 48 and 72 hours after slaughter for samples stored at 4°C. The results pointed that beef muscle (m. semimembranosus ) had the highest water holding capacity 4 hours post mortem (33,68%) and the lowest (-33,45%) 24 hours post morte m. During the ageing process differences in ability of beef tissue to hold native water (filter paper press method) were observed depending on the method of treatment (longitudinally or laterally). Changes in hydration of muscle tissue are probably due to changes in the structure of myofibrillar proteins post mortem . The analysis of photographic documentation made for microstructure of the meat samples demonstrated differences in distances between fibrils and various sarcomere degradation grade.