To predict meat quality after slaughter, biopsy samples were taken from musculus longissimus lumborum et thoracis of live pigs at approximately 40 kg and 80 kg of weight. The obtained values from biopsies for pH1 and EC50 (electric conductivity) were compared with measurements after slaughter at a weight of approximately 110 kg. RYR1 genotypes were determined from blood samples using PCR-RFLP. Mating of Nn sows with two nn boars resulted in 72 Nn and 40 nn offspring. Significant differences between the two genotypes were found for pH1 and EC50 values for the three weights. The coefficients of correlation for the Nn genotype of the RYR1 gene between the values after slaughter and both the first and the second biopsy for pH1 and EC50 were very low (r = 0.06, r = 0.14, and r = 0.26, r = 0.26, P 0.05). For the nn genotype were r = ?0.23, r = ?0.15, and r = ?0.25, r = ?0.11 respectively. The values of pH1 and EC50 were highly correlated (r = ?0.52 to ?0.84, P 0.001) both within biopsies and after slaughter.