Phosphorus nuclear magnetic resonance ((31)P NMR) measurements were made to determine muscle energetic metabolism on muscle biopsy samples of heterozygote malignant hyperthermia (Nn) and normal (NN) pigs DNA tested on occurrence of mutation in RYR 1 gene. Biopsy samples (approx. 1 g) were obtained by spring-loaded biopsy instrument (Biotech, Slovakia) from Longissimus dorsi (LD) muscle at 80 kg live weight. The spectra were recorded at 121 MHz on a VXR 300 (Varian) spectrometer in 10 mm diameter tube (maintained at 39 °C) for 50 min. pH of bioptates after NMR measurements were also measured at 60 min. The changes in inorganic phosphate (Pi), phosophocreatine (PCr) and adenosine triphosphate (ATP) were faster in heterozygote malignant hyperthermia (MH; 29 crossbred White Meaty×Pietrain) than in normal (13 Duroc, Yorkshire and White Meaty). The values of PCr at 20 min and pH at 60 min after taking biopsy allowed discrimination between NN and Nn pigs and significant (P<0.05) differences were also found between two subgroups in heterozygote MH pigs with different rate of post mortem muscle metabolism. The values of PCr and pH as measured at definite time on the biopsies, were significantly (P<0.05) correlated with the rate of post mortem metabolism (pH) and with meat quality traits (r approx. 0.4-0.6). The (31)P NMR measurements pointed to impaired muscle energetic metabolism connected with the occurrence of mutation on the RYR 1 gene in heterozygote MH pigs.