The aim of this study was to compare the diagnostic values of two methods in pork meat quality evaluation, that is, Method I: pH₁ and pH₂₄ and Method II: electrical conductivity (EC₂) and pH₂₄, which included pH₂₄, and their modifications, that is, Method III: pH₁ and pH₄₈ and Method IV: EC₂ and pH₄₈, which included pH₄₈ measurement. Five meat quality classes, namely reddish-pink, firm and non-exudative (RFN), high quality (HQ), pale, soft and exudative (PSE), dark, firm and dry (DFD) and acid meat (AM) were assessed in four even-numbered genetic groups of 40 fatteners each, namely (L×Y)×D-A, (L×Y)×D-B, (L×Y)×H and (L×Y)×(D×P). The change of diagnostic method and therefore pH time measurement from 24 hours to 48 hours post mortem caused a major increase in the percentage of acid meat (AM) that was diagnosed. Most differences were observed in (L×Y)×H fatteners, namely 77.5% between Methods I and III and 75% between Methods II and IV. This increase in AM frequency indicates that as a result of significant changes in the post-mortem metabolism that occur in the meat ageing process pH₄₈ should be regarded as ultimate pH (pH_u).