Stress-sensitivity of pigs determined by recessive gene HALn is known as a significant problem in breeding. The pigs of HALnHALn genotype are stress-susceptible and high percent of these animals develop PSE meat post mortern. The animals of HALN HALN or HALN HALn genotype are stress-resistant and their meat is classified as normal. The HALn gene affects advantageously growth rate, feed conversion ratio and higher lean content. Thus, HALN HALn genotypes are the best material for fattening. The HAL genotype should be defined by molecular method - PCR/RFLP.