Quebec Landrace pigs (n = 896) were halothane tested and blood samples were taken for the determination of Phi, Po2 and Pgd phenotypes. The incidence of the halothane positive pigs was 5.3%. The frequencies of the favorable alleles PhiA, Po2S and PdgA were respectively 29.2%, 39.6% and 64.4%. The highest linkage disequilibrium was found between Hal-Phi (0.0606) followed by Hal-Pgd (0.0428) and Hal-Po2 (-0.0308). Alleles PhiB, PgdB and Po2F were associated respectively with 97%, 81% and 74% of Haln haplotypes. It was concluded that a selection in order to increase the favorable marker loci PhiA and PgdA would reduce the Haln frequency in Quebec Landrace pigs.