The aim of the study was to analyse the influence of tenderising treatments applied to the carcasses of Polish Holstein-Friesian (PHF) bulls of Black-and-White variety on the process of meat tenderisation and to assess the role of collagen in this process. The research was carried out on m. longissimus thoracis et lumborum. The carcasses were subjected to high-voltage electrical stimulation (ES), conditioning (CD), and both treatments together (ES + CD). The carcasses which were only refrigerated were the control group. The content of collagen in meat, its solubility, the share of the polypeptide subunits α1(I)CB7 and α1(I)CB8 of type I collagen and α1(III)CB5 of type III collagen were also analysed. ES with and without CD significantly accelerated the meat tenderisation and increased collagen solubility. CD always caused the degradation of type I collagen subunits, especially the α1(I)CB7 subunit. However, CD had significantly lesser influence on the rate of meat tenderisation than ES.