The aim of this study was to determine sperm membrane integrity and mitochondrial activity, to quantify possible apoptosis, and to investigate relationship between these parameters. Apoptotic-like changes were evaluated using a combination of YO-PRO-1/PI staining, and changes in mitochondrial membrane potential were evaluated using JC-1. Gel-free ejaculates collected from five boars were extended in BTS diluent and stored for six days at 15-17°C. The fluorescence analysis was repeated on the first, third and sixth day of semen storage. Motility was also assessed on each day of the experiment. The percentage of apoptotic sperm detected by YO-PRO-1/PI staining inconsiderable decreased, while number of necrotic sperm increased during six days storage. The percentage of spermatozoa with mitochondrial membrane potential (ΔΨm) dysfunction increased and reached the highest level at day six of semen storage. The ΔΨm analysis by JC-1 revealed that mitochondrial function was highly correlated with both sperm motility (r=0.936) and apoptosis/necrosis evaluated by the YO-PRO-1/PI assay (r=0.960).