The objective of the research study was to determine, based on the dynamics of changes in acidity, the effect of age of horses on the course of muscle glycolysis progressing in horse meat during cold and frozen storage. Samples of the longest dorsal muscle from horse carcasses were analyzed. The animals were divided into three age groups: foals (their age up to 2 years), young horses (their age between 2 and 10 years), and old horses (their age above 10 years). The research comprised 25 carcasses of foals, 35 carcasses of young horses, and 38 carcasses of old horses. The horse meat is characterized by a long-lasting process of glycogenolysis. The characteristic feature of the maturation process of horse meat is a rapid drop in the pH value and long-lasting high acidity; this has a positive effect on the stability of the meat material. In all the age groups analyzed, the horse meat stored under the cold conditions was characterized by low pH values during a period of 120 h. As regards the material stored under the cold conditions, statistically significant (p ≤ 0.01) differences were reported between pH₂₄, pH₄₈, pH₇₂ (to reflect glycolytic changes) of the meat of foals and adult horses depending on the age of the animals, whereas, in the case of the meat material stored under the frozen conditions, such differences (p ≤ 0.01) were found in the same age groups; however, they referred to pH₁ and pH₂₄. In all the age groups, both in the cold stored and frozen stored meet, the process of post mortem glycolysis proceeded in a similar way, except for the meat of foals, in which those transformations proceeded at a slightly lower pH level. In the meat stored under the frozen conditions (1 and 3 months), the decrease in the acidity was more evident and faster compared to the meat material stored under the cold conditions immediately after slaughter.