Cheese in a sack is a Croatian autochthonous hard ewe's milk cheese. Its main specificity is ripening in a sack made of lamb skin. As casein forms the base of cheese structure in which other compounds are incorporated, proteolysis is considered to be the most important process which contributes to the formation of the characteristic cheese texture. Moreover, proteolysis is involved in the formation of a desirable cheese flavour. The aim of this research was to determine physicochemical, proteolytic and textural changes over 30 days of cheese ripening, and correlations between phyiscochemical and proteolitical as well as textural changes of cheese during its ripening in a sack. Research was conducted on 10 batches of cheese which were manufactured at a small-scale dairy farm. From each batch, samples of curd and cheese at 15 and 30 days of ripening were taken. Physicochemical analyses of cheese included determination of pH value, total solids, fat, protein and salt content. The proteolytic changes in cheese were monitored by determining the content of αs1-casein, αs1-I-casein, β-casein, γ- casein, water-soluble nitrogen fraction (WSN %TN) and 12%-trichloroacetic acid soluble nitrogen fraction (TCA-SN %TN) in the total nitrogen, and ripening indexes (alpha and betta). The cheese texture was determined by a compression test. The time of ripening had a significant effect on the observed physicochemical, proteolytic and textural parameters (P<0.05, P<0.01). The content of protein, TCA-SN %TN, index alpha (P<0.05), αs1-casein, β-casein, γ-casein and index betta (P<0.01) correlated significantly with the cheese texture. Proteolysis is very important for achieving the desirable sensorial quality of cheese, which consists of appearance, flavour, colour, odour and texture.